Nice, coherent theme (aggro pirates) you put together with what sounds like a limited collection; I took a moment to look at the deck, here are my first impressions:
I agree, 20 lands is not enough. I think 22 is low as you have 4
evolving wilds (good card to fix your mana when you need red/black) and those basics fetched with
evolving wilds coming in tapped hurts your tempo and you are aggro strategy. 23 with
evolving wilds is where I would start, trim down if I find I'm flooding. I'd cut
traveler's amulet,
orazca relic, and
gruesome fate to add 2 mountains and 1
swamp if you're sticking to basic lands.
I would also consider the following changes based on the cards you said you had:
Cut
gleaming barrier for
forerunner of the coalition - way better fit for your decks aggro strategy, and you can tutor up the pirate you want/need at the time
Cut 1
brazen freebooter for
daring buccaneer - again, a faster play and you should nearly always be able to cast it cheaply with so many pirates
Cut 1
fathom fleet boarder for
moment of craving - this is an underrated spell, as there are lots of
x/2 creatures out there than can be tough to kill in combat
I also think
recover would work well, getting back your best pirate if it
ends up in your graveyard somehow. The changes cut your treasure production, but i think your mana will be smoother this way, and better for an aggro plan. If you really want to keep the treasure, I think you need a payoff for it. Right now it is just temporary ramp, and you don't have much card draw - so the extra mana of the treasure can be a waste if you don't have a card in hand to use.
Cool, ultrabudget deck; thanks for sharing your idea!