A corvette is the best ship for this, focusing your stats on damage will allow you to do this in higher Challenge Levels, speed is still very important. (Yes I know my stats are rubbish for this currently.)

Since we're going to be destroying pirate's defense-towers Explosive Ammunition Coating is the obvious choice for specialised equipment.

Construction Supplies and Advanced Construction Supplies will allow us to build more towers for pirates to capture thus giving us more to blow up.

I recommend a specialist that repairs damage, though a spymaster is also useful because you'll be able to tell which towers are destroyed or repaired by whether or not they remove Fog of War (gray areas on your minimap where you can't see if there are ships or not). If you have one that does both, terrific!

Offensive specialization will speed things up, you'll still have plenty of time for hasty repairs to cooldown if you get shot by pirates occasionally. You should still try to avoid pirates.

Fairly straightforward, tick the "Allow friends to join" option off so you're not bothered by a well-meaning friend who captures everything.

Make sure that "Limited Item Stats" and "Permanent War" options are both ticked off. The region min/maxes in the top right corner control the level scaling or "Challenge Level" of regions during map generation, the challenge level multiplied by 3 is the TP (Talent Points) a player is supposed to have for balanced gameplay, it also determines whether you can access towns in that region. Make sure you put the sliders for "Challenge" and "Battle Damage" to 200%, this will cause more pirates to spawn and decrease the amount of shots it takes to destroy a tower. It can take a bit of trial and error, you want it to be just a high enough challenge level that a tower survives your volley skill with a small sliver of health left.

Since you're creating a new world your fast travel options will be limited since factions haven't spread everywhere, make a small + somewhere on your map.
You only need one faction for this, Valiant is what I prefer due to the combat XP bonus they receive, Sojourn may also be useful for their Speed and Damage bonus. Place the faction in the middle of the +, this will allow you to traverse the border of this starting region into any of the 4 other regions. By default faction starting regions will have a challenge level of 0.

See how the Challenge Level of this region is 50 (150 TP)? It's so high that the normal faction spread that occurs when creating a map does not happen, guaranteeing the region is completely controlled by pirates.

Let's up the Challenge Level by 5 (15 TP), increasing the challenge diversity of the map, you can adjust a region's Challenge Level using your scroll wheel while creating a world.

Let's decrease this one, Challenge Level 45 (135 TP) should be just right for me. Having the other regions at higher Challenge Levels will let me move to those later instead of creating a whole new world.

Let's put this one a little lower just in case the other one is still too high.

Since I have 402 Talent Points I can access towns in regions with Challenge Levels of 134 (402 TP), increasing the Challenge Level to this will cause towns to carry equipment at my level.

PROTIP: Windows in the game are movable, just left-click and drag the top.

Make your way around the map, destroying towers as you go, you will quickly be swarmed by pirates in the beginning, try to get away. Don't capture anything, it will just slow down the pirates repair efforts which will slow down how quickly you can gain xp.

(At 200+ TP you can place buildings on water, greatly increasing the amount of towers a region can have.)
If you see anywhere you can build a tower, BUILD IT, don't wait around for it to construct or help it along, just continue on your merry way.

Avoid pirates as much as possible, at 200% Challenge and Combat Damage they'll quickly destroy you, even at their lower level. Plus destroying pirates will slow their repair efforts, even though they do give pretty good xp it's still faster to destroy towers. When you level up your TP count won't update in the talent window, don't worry, just close and reopen it.

During extended sessions you may make powerleveling less boring by muting Windward and having a music streaming service or a music playlist running in the background.