It depends on your skill level. Sculpting is the common next step when it comes to Character creation, but Poly modeling is more in the realm of Roblox. You may want to check out some of the Character creation modules or even the CONCEPT course. I’d probably Start with Concept then move to Character Design Process. I haven’t watched the second one yet. Although I did like the Piero – Animated Character Concept. Two others that are on my list to watch are Creating Character – Where to start and Creature Concept Design. Rigging and Animation I’d wait until you are comfortable with modeling first since you want to specialize.
***Edit*** Just saw that Kent created a playlist: https://cgcookie.com/playlists/5911-track-character-creation-with-blender
