96 chevy blazer wont stast seems to me not getting gas are spark maybe?? i dont know?

i let it set for 10hrs and it started right up i got to drive it about 20 miles and it died, i let it set for about 3 hrs then it started up and i got it home about 2 miles after that i let it set overnight but when i got in to try to start it it wouldn't. the fuel pump kicks on i even added 2 gallons of gas and a fuel additive. please help maybe a fuel problem? maybe an ignition problem?