Mike, I'd suggest starting with a 3/8" drive set. An adapter makes it easy to use 1/4" drive sockets (carefully), and even 1/2" drive sockets occasionally. It's the most useful size for general stuff.
You definitely want two 10mm box wrenches, and a second 10mm socket is super handy. I've found lots of uses for a good 8" or so pair of channel locks- worth the money in my opinion.
Zip-ties, 10mm box wrench, maybe a multitool, a spare tube and the tools to fix a flat should go with you everywhere. Also, when you first start riding, you should have the wrench that tightens your motor mounts with you. I always make sure there's good tension after riding a few minutes on a new build, and then pretty regularly for a few rides. This could be because I'm smart- or because I'm paranoid. Either way, it works
I often use a 3/8" drive socket (old one) on a 2" extension, to tap with a hammer as I tighten, to get my rear wheels where they need to be in the dropouts for proper chain tension. That socket is usually 15mm. I've never broken one, but you'd better have two just in case.
Pawn shops are great for an extra socket or wrench, usually just a few cents each. Dig around the bin, I find Craftsman and other good stuff for nearly nothing.
Two other things;
I forget... Has anyone mentioned that you would be better served by not using a chain tensioner? At least the kit provided one. If you take your time and get your chains just so, there is usually no need for any tensioner. I never use them and have never had a problem. It's less parts to fail, less parasitic drag, less noise, and less ugly.
Also, have you signed on to the member map? It's a cool feature here.
You're coming along nicely with some real good advice from these folks!
Trey