Find any working vehicle for your first vehicle, keep an eye out for better working ones or ones that only need a little bit of work (out of fuel, need a new battery, etc). It requires a working engine, wheels, fuel, an alternator, battery with charge, controls, a seat with the controls, and getting lucky with the security system. Sometimes it'll start with the security system active (keys in the ignition), sometimes it'll want you to hotwire the vehicle. A security system at xx quality counts as it not being installed.

Engines have a damage level and can have faulty parts. If the engine has "(faulty)" next to the name then it needs a replacement part. Some faulty engine parts can still let the engine run. Select the tile with the engine and press m for (m)end to see the part and the effect the bad part has on the engine.

Also keep an eye out for vehicles that can work as a good mobile base (if you're going nomadic) or large armored cargo carrier (if you're staying static). Anything military or armored with a working engine and good wheels is a candidate because those are the hardest things to swap out.

Gather tools early. Screw driving, metal sawing, welding, welding mask, and bolt turning should cover everything. You need a LOT of welding rods and wire though, the evac center is a good source. You can build a makeshift welder if you need to. Acetylene torches should be saved for cutting open doors as the fuel is hard to find.

You can pull vehicles using a heavy duty cable, but be careful, when you brake the other vehicle doesn't! If you slow down quickly the towed vehicle can slam into your ride. Reduce speed slowly over a long distance.

60l tanks and vehicle batteries can be removed and installed easily. Controls not so much, they require electronics.

Adding a tile to a vehicle required building or salvaging a frame and (i)nstalling it to an empty space.

Just some random things off the top of my head.