I like being a tank! But...

...I'm new-ish to this game, so when I queue for dungeons, I'm not 100% used to the layout or anything, especially new dungeons. I end up feeling like I'm messing up my team by not doing big enough pulls, accidentally turning off my tank stance, or just not knowing which way to go when I'm meant to lead. Should I just be doing my homework by researching each new dungeon? (Tried this on Haukke Manor yesterday and it went mostly fine outside of a couple mistakes on my part) or should I play a different class, like a dps? (I like summoner, queue times are kinda annoying though.)

Edit: my phone notifications broke after like 8 minutes, thanks for all the answers and support guys! I have a better outlook on tanking now :-)