Right now antimatter is the most powerful fuel we know of. Only a few grams is needed to reach Mars. But even with warp drive it would still take a lot to send anyone to other planets unless there is another means to generate antimatter that wouldn't break the bank.
Someone said a quantum singularity -- a black hole -- where it shreds matter into energy, rather it belches out streams of matter from its poles. One pole is facing away from the ship out the nozzle to provide primary thrust, the other heads into the ship where with a powerful enough magnetic shield can be deflected out the aft providing even more thrust.
Even though interstellar hydrogen can be used to accelerate to light speed, hydrogen density is still pretty small where it's only one atom per cubic centimetre.
In fact a proton -- plus an electron gives you one hydrogen atom -- only has a mass of 1.67x10^-27kg. Even if we have a 1km diameter ramscoop and traveling one light year, that's 7.4253x10^28 cubic centimetres.
Then when you do the formula of D=M/V or M=DV where the density is one atom per cubic centimetre times it by the volume of a 1km diameter ramscoop and 1 light year, that's only a mass of 124kg in one light year.
Sounds like warp drive is becoming more and more ideal once we get more of an idea about gravity waves and such, or put on a quantum singularity on the back end of a comet and use the comet for fuel.