That rocket is pretty inefficient, and the design of it could make it hard to fly. It probably can reach the moon with plenty of ∆V to spare, but you could make a rocket that's easily capable of a mars mission in the same space. I'll leave some tips and an example of an improved rocket for you.
- Use vertical separators under engines, not side separators
- Use more efficient engines on your upper stage
- Make every part of your booster the same diameter
- Don't put side boosters on top of side boosters
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You'll find this rocket to be more efficient and easier to fly. I tried to use your style of building, but this is just a single example. There are millions of unique (and useful) rockets you can build if you practice and find what works!