At Lvl 10 take whichever ultimate you prefer, generally Ravenous Spirit will be better, you can use it from far away and it deals a lot of damage and is hard to escape.

At Lvl 13 I'd always suggest Ice Block because I myself love the effect and the uses it can have, though, if you don't want the extra active button, take Superstition against magical damage and Guardian Toads against physical damage.

At Lvl 16 I prefer Soul Harvest cause I am aggressive and love to go into enemies and their waves to get 35% more damage and health. If you are good with Zombie wall Ring of Poison is a deadly choice.

At Lvl 20, upgrade ultimate or take Vile Infection, if you can reach 175 stacks, Vile Infection will by far be the strongest pick.

At Lvl 4, if you're confident in hitting your spiders all the time, take Hexed Crawlers, if you're playing the long game, take Big Voodoo.

At Lvl 10 take whichever ultimate you prefer, generally Ravenous Spirit will be better, you can use it from far away and it deals a lot of damage and is hard to escape.

At Lvl 13 I'd always suggest Ice Block because I myself love the effect and the uses it can have, though, if you don't want the extra active button, take Superstition against magical damage and Guardian Toads against physical damage.

At Lvl 16 I prefer Soul Harvest cause I am aggressive and love to go into enemies and their waves to get 35% more damage and health, this will also increase Spiders damage, as they are magic based. If you are good with Zombie wall Ring of Poison is a deadly choice.
I'd never take Spider Colony, simply because it has no effect, whatsoever on your spiders and their strength.

At Lvl 20, upgrade ultimate or take Vile Infection, if you can reach 175 stacks, Vile Infection will by far be the strongest pick.