Definitely read the stickies. There is a LOT of information there.
But if you just want a mix to get you going you can use Flourish and/or some root tabs (tuck them under the substrate at the base of your plants) you can find these at your local LFS
and sometimes even walmart. Many here use dry ferts mainly because it is a lot cheaper long term and the ability to adjust individual elements is nice.
I just got into planting my tank last year and I was intimidated at first with all of the information there is to read and learn but once you get the hang of it, it is pretty easy.
Don't underestimate the power of water changes to add essential elements back into the tank as well.
A lot depends on your specific tank set up so you should post your tank size, light specs, substrate, and frequency of water changes and pictures if you can since different symptoms can indicate different problems.
There are a lot of brilliant folks here with a lot of experience to help you.
A lot of times the plants you get at the LFS
have to recover from improper conditions when you get them home. Don't give up! You might even be able to have some on here send you some healthy plants that are practically indestrucable. Many of us need somewhere to send our trimmings.
Good Luck! It takes some work in the beginning but it is worth it IMO