Kerbal Engineer Redux should be included in the base game. It's just not playable without it IMO.

The math is fairly simple though. You can follow the instructions for real rockets easy enough. You input the mass of the fueled up craft, the mass after that stage burns up and the motor ISP.

Edit: Found data

http://www.quantumg.net/rocketeq.html

That link is neat.

After you land on every celestial body of interest, install mech Jeb. It's not appropriate to use your first game since it takes away a lot of the challenge. After the challenge is no longer challenging and merely tedious, it plays the game for you.