My main advice would be to not worry about it too much, a lot of people try to jump in two-footed and create a video game experience when they don't have the experience with the platform to be able to do it. Treat the VTT like an actual table top, you might start with simple line drawing maps and tokens and use the platform to assist with dice rolling and visual necessities... you might even trust your players to continue using physical dice and just use the VTT for maps and character sheets (or they could even use physical sheets still to!). It can be as involved as you want, but overall your own experience with Roll20 will dictate how far you go with it. Check out the tutorial (hella broken but still some good stuff in there) and make a test game to play around in. Use the forums (the search sucks but google can help there) and ask questions rather than get stuck for hours, this community lives to support :)