I recommend you to just start building a game,you will learn alot making games.(at least I did) First, try making simple ones,learning the basics of the engine your using,then you can try making more difficult games and editing the engine. (adding gimmiks,etc).You will learn most of the stuff by looking how it is coded,and you should just try playing around a bit.
using engines is simple too,just start building a game on top of it,by making your own graphics,sprites and levels and if you have a bit more experience you can edit the engine how you want it.(as long as it follows the rules the engine creator has given)
I'd first recommend using a more simple engine,but you can directly start with SDASH if you want,though it might be hard to understans if you are a beginner. :/
I'm still kind of new to fangaming and I'm not a pro,but hope this little advice may help you out a bit.~|