Either way, you need the basic 1/4", 3/8", 1/2" socket sets. 1/2" should go up to about an inch and a half. 1/2" impact. Get the wrench set up to 1 7/8. (Metric equivalents as a lot of stuff is metric now). Screwdrivers, hammers, pry bars, multimeter.
If working on trucks, you can get by doing brakes with a screwdriver. Eventually you can get the tools, but they arent cheap.
Most likely you wont have to go bigger than 2" on semis, with the exception of wheel hub nuts. If you get into construction stuff, you will be better off going to 3".