I've had a flute for a few years ago, and I know majority of the flute fingerings(like 95% of them), but I'm not the best flute player( i can barley play). I also cannot afford private lessons. Is there any tips/exercises I can do to get better?

Practice! You can't get better without practice! Knowing fingerings is a good start, but there's so much more to learn, such as how to use your air to produce the best possible tone, how to get your tongue working with your fingers, etc. etc., and these things only come from experience. You might also have the flute checked to be sure it's in good playing condition (if it's full of leaks, that could be a big reason why you can barely play). Working through etudes and various other exercises will help a lot too. There are a huge number of these available, focusing on everything from finger facility to tone.

I found a lovely book called "How to love your flute" by Mark Shepherd has ALOT of great info in it. It covers everything from flute history, to basic care and repairs to techniques on playing. (Personally I find the title somewhat silly and think it might sell better under a different name.) It also covers different types as flutes as well and is very in depth.

You mention not being able to afford lessons. How about just getting a couple to start you off in the right direction?

Good luck.