Mid tier Strength, Intelligence, and Charisma are what I'd suggest. Knowing what it takes to repair and maintain armor and how many resources you have coming in to cover that is also vital.
My current character is a PA specialist. Once I got the T-45 from Concord, I got the various Fusion Cores (FCs) from the easy to get places and starting with Lexington and Super Duper Mart, it was all Power Armor, all the time. I put some miles on that T-45 set before I found my first T-51.
Strength is important because - Armorer is essential to upgrading your armor, and Strong Back is needed to bring home the resources that upgrading everything can cost.
Intelligence is important because - Science! is vital to power armor use. Without it, you will never have the extra systems and will remain a low letter grade variant. If you want to really spiff out a suit of T-60 or X-01, you will really need it. Scrapper is hugely important to making sure you get the materials you need from saluaging.
Charisma is important because - Local Leader helps you build up the network of settlements to keep the resources flowing. With multiple water purifiers (industrial sized) in one settlement you can use the purified water it creates to trade for either a) expensive heavy gunner ammo or
rare crafting materials like circuitry and copper (heavily used in armor upgrades and repair).
Endurance is not bad to have either, as Aquaboy/girl synergizes well with your ability to walk along the bottom of standing water areas and even just walk out to Spectacle Island.
Once you get your T-45 from Concord and get back to Sanctuary, get it fully repaired. It requires only Steel to repair aside from the Torso (which requires 1 Circuitry), so scrapping the environmental stuff in Sanctuary should give you enough. Use your Pip Boy to mark the following components (switch to the component view of your junk tab in inventory before emptying your load of stuff from the History museum): Circuitry, Fiber Optics, Copper, Nuclear Material, Adhesive, Aluminum. Ceramic is a good idea, too, as is Crystal.
You will eat a ton of Aluminum throughout using your PA. It is vital to gather as much as you can. The best things to get it from (due to low carry weight) are: Aluminum Cans, TV Dinner Trays, Surgical Trays, Aluminum Trays, Trays, Aluminum Cannisters, and Toy Rockets.
Grab all the FCs you can before you go down to Lexington. You'll be out of your armor and likely just wearing leather scavenged off Raiders and using whatever guns you have. That's fine. Here are some easy to grab ones:
1. Museum -- You should already have it by doing the quest.
2. Mole Rat Den beneath the Red Rocket -- Go in back of the Red Rocket outside Sanctuary and there's a den. Clear it of mole rats and it should be on the ground down one direction.
3. Concord Civic Access -- The hole that the Deathclaw jumped out of? Yeah. There are some radroaches, molerats, and a couple lowbie mirelurks down there. Kill them, pick up everything, near the end is a fusion core on the ground.
4. Abernathy Farm -> USAF Station Olivia -- Head W/SW from Red Rocket and talk to the Abernathys. Get the quest to get their daughter's locket and then go up the radar station. Kill your way through it (being careful of Ack-Ack's minigun) and get the Fusion Core at the lowest level. There are like 10 raiders in the whole place. Easy.
5. Robotic Salvage Yard -- On the way to Station Olivia, follow the lake/river that separates Sanctuary from the rest of the map. You'll find the salvage yard. There's a shut down Sentrybot and a small building with some loot. Get the magazine on the table for a slick flames paint job for your power armor (Full suit painted is +1 Agility and costs no resources -- great starting paint job). Go to the sentrybot and loot the steamer trunk next to him of gear and then grab the programming holotape. Run the program on your Pip Boy and order it to self destruct (stand back for this). Loot the wreckage -- Missiles, Fusion Cores, Steel, Aluminum. Everything that makes a growing Power Armor big and strong.
6. Federal Ration Stockpile -- Turn in your quest from Station Olivia at the Abernathy's and then go west/southwest. Look for a church. There's a hatch into the Federal Ration Stockpile there. You don't have to go in, though. Go SE of the church and you'll see the stockpile. It's covered in raiders and, but behind an outlying building is an FC generator. You can, with caution, sneak up and nab it as it faces away from the encampment. You can also murder everything there and enjoy your loot and XP.
As a note, for these locales there are two suits of power armor additional you can grab if you want. West of Station Olivia (almost directly between the Robotic Salvage Yard and the Station is a crashed vertibird. There will be a partial suit standing next to it. Loot the armor off it, or insert a core and fast travel it back to Sanctuary and bank it. West of the Federal Ration Stockpile is a semi box trailer and inside is another suit. You have to be sneaky to grab it, as the raiders know about it and will grab it if alerted. This one has a core in it, but the other near the vertibird does not.
After that, you have several Fusion Cores and a spiffy suit of T-45 with a sweet as heck red flames paint job. Do the quest that Preston gives you to help Tenpines. They'll send you to Corvega. Grab the armor, head to Lexington and first go into the Super Duper Mart. Do some feral ghoul stomping and then grab the FC out of the generator in the back room.
Avoid the raider with the Fat Man in mid town until you can get a killshot on him, and then grab his Fatman for later in the game and any gear/ammo he and his buddy had. Head to Corvega and start busting skulls (and don't forget to grab the FC from the generator inside).
T-45 lasted me till level 20 doing this. Upgrade it as much as you can and don't be afraid to expend resources on it. It's keeping you alive after all. As soon as you can grab a full T-51 suit from somewhere, do so. The T-45 armor suit is about 75% as much protection as T-51 offers, so it's a big upgrade (T-51 to T-60 isn't as big an upgrade, but X-01 is). There should be a full suit of that by the time you get to the National Guard Training Yard if you stick to the North side of the map (Cambridge and up), and if you venture out to Nahant, there's a barge guarded by robots that will require you to have Expert lockpicking to open and it should spawn as T-51.
Good luck!