If you are on a tight budget, I will assume that your pack, tent, and sleeping bag must stay the same for now.
Your pack isn’t bad, but it has a lot of volume so resist the temptation to fill it up.
Your tent isn’t all that light, but reasonable for a double wall solo tent.
That Kelty will probably be fine for summer use. Any idea what it weighs? Is it down or synthetic?
My first recommendation would be to buy a scale and make a spreadsheet of all of your gear. You should list everything that goes in your pack no matter how small or insignificant. You would be surprised how much weight can be saved in the “little things”.
I would replace that Stuff Sack/Pillow with a lighter weight stuff sack. I am assuming that you are using this for your sleeping bag, so with the large volume of your pack, I would get a large stuff sack. That way you can compress it smaller when you pack is full of food, but as your food bag gets smaller, your sleeping bag will expand to take up more space. Campmor sells an Equinox 8x18 Sil stuff sack for an affordable price that is less than an ounce.
I would either drop the esibit stove or the Lite Max. You don’t need two stoves.
Do you actually plan on using a frying pan on your trips? If not just take the pot part of your combo, or buy a small solo cook pot. Antigravity Gear sells a nice solo pot for something like $12. You might even pick up a Caldera Cone to use as a stove from them too and drop both the esibit and canister stove.
I am not going to say not to take the GPS, as it probably depends on where you are going. If it is on maintained trails, it is probably not necessary, but you might be going somewhere that it would be helpful.
What are you carrying this tarp for? If it is a cheap blue tarp it is probably heavy as heck so I recommend you drop it.
I prefer a headlamp over a flashlight but that is a personal preference. You wouldn’t save any weight going to a cheap light headlamp like the Black Diamond Gizmo. You could save some weight by going to a Photon Freedom or other similar light.
I would replace the heavy leatherman with a light knife like the Spyderco Ladybug or smallest 0.6oz Swiss Army Knife.
Ponchos are light rain gear for the summer, but realize that they are terrible in the wind. I don’t know what kind of weather you will be hiking in, but keep that in mind. If you are using something like the Gatewood Cape or Golite Poncho Tarp, you could also use this as your shelter.
You ask about a waterproof jacket as well. If you are going to take a waterproof jacket then what are you planning to do with your Poncho. You shouldn’t need both.
I don’t think you want a waterproof and warm jacket. You want a seprate waterproof shell and insulating layer. REI currently has the Marmot Essence on sale. It weighs 6.4oz for a Medium. DriDucks (5.1oz) jackets have also worked well for me for on trail use and they are cheap, but you have to be careful with them and they are cut huge so buy at least one size smaller than normal.
As for an insulating layer, Fleece is always good on a budget but isn’t real light or compressible. Polartec brand fleece is better than the cheap stuff and Campmor, LLBean, and Cabelas all sell cheap Polartec jackets that should be in the 15oz range. If you want something lighter check out the Mont-Bell UL Down Inner Jacket or the Patagonia Nano Puff.
I hate to see people use iodine as water treatment as I know it can cause health problems. I recommend Aquamira repackaged in mini dropper bottles, but some long distance hikers use bleech.