my two cents:
you've got to figure out what format is best for you. That doesn't necessarily just mean the one that you think that you're best at. It might be that one format fits in with your life better than another.
For me I started out playing SNG's but I quickly found out that they tilted me a lot me than cash games because you can invest a lot of time in SNG's only to have something interfere and have to sit out. I found cash games a lot more convenient because I can sit in and out whenever I want.
In terms of developing your game you may initially want to visit schnitzelfish's productivity thread. Amongst a lot of other great info there are good tips on how to structure your learning and maximise it. This might give you a framework for approaching learning.
One way I would recommend approching it is to:
Read some strategy articles (use the strategy section guides to :give you some structure)
Watch a video
Prepare for a play session ( make some strategy / mindset focuses for the session)
Play a session ( marking hands for review at a later date)
Review the session and post hands
write down areas for improvement
Rinse and repat this process focusing on the areas for improvement (leaks)
This is the approach I used to take. Have been real lazy recently. But ths worked best for me at least.
Hope this helps.