If you start as a Breton you get summon Familiar right away. They also get a bonus towards Conjuration, so that will help you get started.
If you join the mages guild then you can not only buy all available conjuration spells from the conjuration trainer there (once you reach the right level) but you can also befriend your fellow mages, who will follow you one at a time if you do a quest for each of them.
Now you have 1 pet, and 1 follower. However, your follower can summon pets as well! That brings you to 2 pets (yours and your follower's) and a follower, so now you are a party of 4.
There are several dogs in the game that can follow you besides having a human(oid) follower, pick one up and you have a party of 5.
At level 100 of conjuration you can learn to double-summon or raise, so you'll have 2 permanent pets/zombie-slaves. That makes 6.
However (and now it gets silly) you can raise two summoner mages who will summon Frost Atronachs for themselves! That makes 8.
If you equip them with a staff of summoning before you raise them, they should use those staffs once raised from the dead, which leads to a party of 10.
And if you were feeling really generous, you could give your companion a staff like that too. Party of 11!
Now your framerates have probably crawled to a halt, but your group will steamroller over everything.
Most excellent post for any Conjuror initiate. If you like watching your pets et. la. play with their toy soldiers then Skyrim can feed your need. I actually forgot that my Breton could summon a spirit wolf until I read this post...even after writing my post...because I navigated toward being a warrior with two handed axe and dragonplate armor.