Welcome to the forum!

You have acquired a nice selection of trains. You need to purchase some "0" gauge track (not 027).  A postwar ZW transformer would be recommended to power the trains and accessories you have. You would also need a few Lockons and some hookup wire.
For the trains themselves, clean any external dirt and grease with naphtha (lighter fluid). Clean all wheels and pick up rollers with the naphtha also. Oil all loco axle bearings, and the wheel bearings on all rolling stock with a hobby oil. Grease the gears on the locos with a hobby grease. If you buy used track, clean any rust on it with a Scotchbrite  pad. Do not use sandpaper, as it will remove the tin coating. Clean off any dirt and residue with naphtha. Pay attention to the connection pins in the track, as they need to be clean and rust free.
Once you get your track and transformer assembled and the trains cleaned and lubricated, you can start running them . Any problems can be addressed in the future.

Larry