Oooh, the possibilities!

I'd get a female het pied if you're on a budget. Or a female pied if you're not. A female het albino if you're on a budget, or a female albino if you have a little more to spend. That way you could work with the recessives right away. With a female pied you could make 100% het pied spiders or lessers and have some good things to build on further down the road.

With a male lesser, it would be a shame not to get a female something or another in the BEL complex so that you can make white snakes. Mojo, butter, lesser--you've got several choices in there. Double codoms would be great if you have the bucks for it. Since you're working with limited rack space it would give you the most bang for each breeding without producing a lot of normals. A female BEL could crank out some great hets to cross back into pied, and it could make some nifty things crossed with your spider, and no normals. And BELs with your lesser. A female mojo, lesser, or butter with an additional pastel gene would be very versatile.

The biggest hole I see in your genetic deck so far is no pastels. Those mix well with so many things. A female pastel can get you bumblebees, pastel lessers, pastel het pieds. A female pastel yb would give you all sorts of options if you want to spring for it. A female superpastel would be awesome. Pastel het pieds, bumblebees, pastel lessers, and no normals.

With your limited space, I wouldn't get any more males until I had my females bought and added some cage space for more females.

Since you only have 3 slots open at the moment if it were me picking 3 snakes, I'd go for

1) Female pied; het pied would work well if it carries another useful gene like pastel, a BEL codom, or spider.
2) Female BEL or a pastel combo with one of the BEL complex morphs.
3) Female superpastel or pastel yb.

and I'd be working on getting more cage space and putting a female albino and a female cinnamon or black pastel on the "to do" list for later on. Once you start producing some offspring from your initial breeding groups you can trade for a bigger variety of females. You can replace your original spider and lesser male with a double gene male you've produced on down the road and have even more to work with. Those are just my thoughts on it. You know what you like and there really is no wrong thing to do--just choices.