Backpacking gear is crazy expensive.
How to save when the budget is tight?
Make your list and see what you already have on hand.
Any clothes you are thinking of taking do this:
Don't even bother with cotton.
Wash your options and then lay them around the house or on a line to dry. Anything not dry in 2 hours in the sun or overnight in the house, leave at home. Anything that feels exceedingly heavy wet, leave at home. You will be hauling it around wet at some point.
You WILL break and lose things while backpacking. Especially when you are first starting out and before you get your packing routine down, so I recommend everyone, including folks not on a tight budget, go the budget route to some extent. Losing a $12 headlamp isn't as bad a hit as the $60 one!
Bras and underwear are a big deal, if you wear them. Some women forgo both while backpacking. I have the letter E in my bra size. Bra non-optional! Sports bras in full-figured sizes are around $50. So, off to Dollar General where they have very lightweight polyester sports bras for $7 that last through 6 months of steady use and dry in minutes and hold the girls steady enough to avoid discomfort. They DO get soaked through with sweat, so I carry a couple extra in case I need to change midday for personal comfort. Quick rinse, clip it to the pack, keep on walking. Same with underwear, I get the seamless undies from DG and they also rinse and dry quickly. If I am going to be gone a few days, I wear bamboo. They are antimicrobial and fairly cheap if you get them online ahead of time.
Socks-wool. Find them however you can and be SURE they fit well and are not baggy. I buy boys socks, even with a size 7-8 foot, to ensure they are snug because a sock for size 7 to 9 is made to fit someone size 9. Keep your toenails short all the time but especially ahead of a backpacking trip. It will save your socks and could save your toenails. 3 pairs. One to wear, one to have clean and dry and one to be drying on your pack, I usually whack the used socks on a tree or rock a few times, turn it inside out and do the same, then let it air out really well. If they are filthy, I will wash them out with some water and a couple drops of camp soap. Otherwise, I good whack-n-air will have them back in hiking shape.
Liner socks with toes work like magic to keep blisters from forming when you have overlapping toes. These are worth the expense, your feet will make or break your hike and the best socks you can afford are what you should go with. Look for sales. Inijini, Darn Tough, Thorlo and nearly any merino wool and merino wool and silk blends are good socks. The wool socks in bundles from Sams Club or Costco will work for a whole hiking season. They are the only socks I have walked holes in, though.
I also have a pair of fuzzy house socks for sleeping in. Most people just use their clean pair to sleep in, but I like a loose cozy sock for sleep. If you do, too, bring it. It's your hike. Most of your 'luxury' weight (optional things you decide are worth carrying) will probably be related to getting decent rest. It's more vital than decent food on the trail.
Good rain gear. The basic rain set from Frogg Toggs is around $20 and is light, packs smallish and works. It's also HOT to hike in and every time I have used mine, I end up with a sweat soaked shirt. So, I just use the pants and use a poncho to cover my upper half and pack. Some ladies hike in a rain kilt or skirt. I have yet to find one that keeps my lower legs dry and I really dislike a wet sock and shoe and mud splashes up on my lower legs-no fun! If you are not hiking in heavy cover, an umbrella can be a good alternate piece of rain gear to combine with rain pants. It will keep the sun off as well.
To keep your pack contents dry, line your pack with a COMPACTOR (not contractor) bag. You can add a pack cover to the outside as well, or use your poncho to cover it. Think about the doodads you will have in the outer pockets not in the body of the pack-map, light, first aid, snacks, camera/phone...plan ahead so you have those items in a Ziploc at the very least.
Sun hat, sock hat, easy enough. Just use your favorite mowing hat or the hat you wear at the beach. Make a knit hat or buy one at Wal-Mart. These are not items that need to be pricey. If you make your own, you can make it match your pack, a truly dorky move that I encourage. I had a mental 'thing' a couple years ago and made about 30 hats, it's not even remotely difficult.
You can use your regular sunscreen, bug spray, chapstick and first aid supplies. You'll want to add moleskin to your first aid kit. Look for them in travel sizes. For staying clean, use baby wipes from home, just lay them out to dry out, pack them up and then wet to use at camp. You can then re-dry them out to pack back out. Anything wet is heavier than anything dry-every single time. Do not leave wipes in the woods! Even in a hole.
Flashlight-go for the lightest LED headlamp with the most lumens that you can afford. There are some good options for $12 out there.
Backpacking towels-go to Dollar Tree and get a microfiber car wash towel for $1. Or get several and use one for a washcloth and the other to dry with. Some folks just use a bandanna, but I like the softy-soft towel.
PUD-grab a small angled oil change funnel for a buck while you are getting your towel. A hard sided funnel won't warp or collapse. Just cut the end off to personal length preference with a serrated knife and go. A pee funnel keeps you from having to take off your pack and your pants down to pee. Some trails lack underbrush and big rocks to give you any privacy. A hiking skirt would be good in this situation
If you have a wicking shirt that needs to be retired, cut it into big squares and use those as pee rags. A pee rag clips to your pack and that's what you use to wipe with, then hang it back up to dry. No TP to deal with packing out! It dries fast, can be rinsed at camp and does not hold odor. Some folks swear the sun hitting them kills all the germs, but I just know that they work really well and means there's less trash in your pack or if you are a total asshat, litter in the woods.
You'll need 2 kinds of footwear-hiking shoes and camp shoes. Camp shoes can be any lightweight shoe that you put on while in camp, Crocs are very popular and knock-off Crocs are pretty cheap, too. Flipflops will work, but in general, a shoe that covers the toes is better-one of the reasons you wear a camp shoe (other than to give your feet a break and air out your boots) is to protect your toes from stubbing and to slip on for that middle of the night potty run. Some folks use a river sandal for their camp shoe and this is a good option if you will be crossing lots of creeks and need to wade. Crocs would be useless as water shoes, going barefoot is dangerous and wearing wet boots all day is misery. River sandals can also weigh as much as a pound each, so plan accordingly. It may be worth it for safety on some trips. Lightweight trail runners are also a good option, they make them out of what feels like hollow foam these days that just weigh ounces each. You can often find them on sale for under $30 if you are not picky about color.
Hiking shoes-Chances are you are a hiker heading into being a backpacker, so start off with what you already hike in unless you know you need the ankle support of a boot to carry a load. Anything that feels good and has good support is a perfect choice. After a few trips, you will have a much better idea what type footwear you will need and you can start looking then. Don't go buy brand new boots with hiking the entire AT in mind, use what you have or what you can buy to also use in your every day and see how far that gets you.
You can go a long, long way on Ramen and Snickers and jerky. Don't worry about $$$ backpacking meals if you aren't going to be out for a week or more with no way to resupply. Which is RARE, I will just go ahead and say it: There are few long trails a beginner would tackle that don't pass near towns, so don't sweat backpacking meals. Lipton cup of soup, ramen, hot chocolate, candy bars, protein bars, dried fruit, foil packs of tuna, chicken and salmon, pasta sides in pouches, instant potatoes-all of these you can find at even the smallest of grocery stores and they are all easy to pack, cook and consume. On a 3-4 day hike, you are not going to run short of nutrients of drop dead from scurvy if you don't have prepackaged meals. Cheese, boiled eggs and avocado all pack well, if heavy. Don't limit yourself to just what's freeze dried, try out lots options! You can dehydrate foods in your oven if you think you want to try it yourself before you buy a special dehydrator that you may decide is not worth the space. Vegan, Paleo and gluten free diets can all be accommodated with regular grocery store food even for several days of hiking, get some goodie to look forward to and slog through with the staples.