here's a nice little thing that gets me to the mun and minmus. (Minmus is alot harder though, you REALLY have to conserve fuel, and I dont think i've ever have got back to kerbin using this design. Try things!)
pod (1 kerbal)
small striped fuel tank (with 4 landing legs and a ladder!)
smallest engine
decoupler
Advanced SAS module
three liquid fuel tanks (blue striped)
largest engine (not the big big one, i mean the fatter one that fits on the striped tanks)
and on the side, 4 radial decouplers with 3 striped fuel tanks and the fatter engine.
Tie them together and it should get you there, i dont know about back though.
Don't ask me how I got to Duna though, too complicated and it took me alot of luck to do it, and I'm pretty sure I just got lucky that my parachute didnt bust when i was falling at about 400 mps, but its the same basic design. You don't need to make the most powerful rocket you can, its mainly how you consume your fuel.
im off to eat someones parents. Try to get to Laythe, cya.