I'm afraid such a general question is just too hard to answer. I'm pretty sure that Litespeed had a few revisions of the Tuscany so I'm not sure what you would want or need. For my build Shimano 105 was the best bang for the buck but you may want something more high end. Contrary to your observation, I can get at least 25 tires and probably 28s in there. Mine came with a Look fork but you might have something different.

My biggest piece of advice would be to pick a groupset and get all the parts as a package. That way you'll know they will work together. The second biggest piece of advice would be to double check any required tools. You'll notice in the thread above that I got lots of good advice around bottom bracket tools.

If this is your first project bike, expect to put in a significant amount of time learning how to properly install and adjust both the front and rear derailleurs. If you decide on a Shimano groupset, read every Dealer Manual for each part at least 3 times before you attempt to install it. Go here for the manuals; the ones that start with "DM" are the ones you want. YouTube is your friend as is the Park Tools web site.

This forum is also a great resource but if you come across a problem ask a specific question to get a specific answer. Good luck!