It seems there's no faster way to gain xp for your dwellers than to make it deep into the wasteland while exploring. However, I always put my new dwellers to work before training up their stats because at a low level they're vulnerable to having their health depleted before I cam heal them. What is the fastest way to level a character up to lvls 20-30? If I stack a room with my best workers so the time between gathering resources is faster, will the xp come faster? Is the xp directly tied to the resources the room gathers or just the overall time spent working the room?

I send my level 1s out to the wasteland with 8+ RadAways and Stimpaks, as I've found that is by far the fastest way to level. With a high number of provisions, they don't run much risk of death if you don't forget about them completely.

Yeah, I agree. Sending them to the wasteland really is the best way....