Car not starting up right

Check the actual fuel pressure if its within specification with a fuel pressure tester-start here

Well I can't really check the fuel pressure because I don't know nothing about cars. I had a few friends checked it out and they said that it might be the throttle going bad, or just bad wiring. Then again they said it might be the main relay. Btw the gas meter isn't working right too. It's been full since last week, is that also a cause for it? Sorry for asking so much im still alittle new to cars

Lets go step by step here-Do the fuel pressure check come back with the readings and then will go from there-possibly could be the main relay or the ignition switch which is a recall -The fuel gauge has nothing to do with it-

http://www.2carpros.com/articles/car-cranks-but-wont-start

Go through aboe and find out what is missing.

Possibilities are plenty and guessing does nnot come to a conclusion.