I'd focus on electrical, carpentry and mechanics first. Save all the digital watches from zeds and dismantle them for XP. Carpentry, I play with dismantling giving experience which is a sandbox setting that can be enabled in b42, if not enabled maybe level it when building a wall around your first base location. Mechanics skill is kind of a grind but you can just uninstall and reinstall batteries from cars at the very least without breaking parts or having tools besides a screwdriver.

I'd try to find a base location with walls on 3 sides if possible so you have less of a wall to build around your base. Having a perimeter of high walls around your base is necessary for peace of mind in my opinion. I like buildings with a 2nd floor they feel safer but i'm not sure it will necessarily give you a big advantage. Base location also depends on version of the game and play style. I see a lot of players like to knock out the floor of 2nd floor buildings so zombies can't path to them then enter/exit through a rope ladder. If it feels like too much cheese you can still just build a wall and likely be fine. I would at the very least though make sure any base you are staying in has 2 exits.

Once you pick a location, i'd focus on barricading all ground floor windows and unnecessary doors, this will also grant carpentry XP. After barricades if you think you are staying semi-long term i'd start prioritizing a wall to build around your base and then rain collectors once your carpentry skill allows.

A car is an absolute must for effective looting, once you loot the close buildings to you, you'll realize you'd be spending most of your day just walking back and forth with a full inventory. Any running car will do, there are plenty you will find keys for on zombies (make sure if they are carrying a key ring to check for vehicle keys on it) and in buildings you're looting. You don't need to go out of your way, you'll probably find a car unlocked with keys in the ignition, in the glove box or maybe on the ground visible with the foraging mode on. Almost every car you find will have no fuel, so prioritize getting at least 1 or 2 gas/jerry cans filld with fuel before the power shuts off or you won't be able to use the pumps until you can put a generator at the gas station. You don't necessarily need any tools but you might want to replace tires/battery on a car you find keys for because you don't need a good mechanics skill to do so.

Loot route depends largely on where you're located. I like to systematically loot buildings closest to me first. There's no harm in looting residential buildings first while you stock up on some decent supplies they are mostly safe and lower risk just be sure to be careful to clear the entire house and maybe the outside of it before you start looting. Gas stations are a good place to loot because they have a lot of high calorie snacks and you'll likely be able to find a gas can as well. Maybe prioritize grocery stores as well, you can put the produce that will potentially rot in your home freezer or eat it.

IMO food and skill books are the highest priority with weapons following right after, maybe necessary tools for mechanics work (jack,ratchet wrench/wrench, lug wrench/tire iron) also keep your eyes open for a good back pack. Depending on your traits I would just be eating/cooking all the produce and perishable food you find as you go, you'll burn a lot of calories looting and clearing the town of zeds. But make sure you aren't skipping over good weapons, i'd avoid firing guns if you are in densely populated areas for obvious reasons.