Store the pixels somewhere so I don’t lose them when I die

Exploring the surface for large buildings can prove quite fruitful, as many of the chests and containers therein will contain large caches of pixels. Take them. All of them. As of right now (shortly after the Frustrated Koala update), NPCs don't even get mad if you take their stuff from their containers.

If you cant' find such structures easily, there's another way to find large pixel caches.

Dig deeper down.

The world I am on has a huge underground cavern that has tons and TONS of capsules full of pixels. dig down deep enough, and you'll start running into them all over the place.

This area is dangerous though, so be prepared.

For extra bits, make sure you kill monsters with a strong Melee weapon, which provides a high chance of them dropping bits (with ranged weapons, the chance for bits to drop is lower due to a higher chance to drop meat and leather instead).

Currently cotton plants are the only viable way to obtain cotton. You also need cotton to craft the tier II armors, so you should get several of them.

When you plant your cotton plants (or any crop, for that matter) outside on a planet with frequent rain you don't need to water them yourself. So you can just go exploring while your farm keeps growing on its own.