Well, you could take regular evocation and simply have the conjuring bit be flavor. So where others throw a fireball, you conjure a sword, slice your opponent with it and it dissolves right after. Where Harry throws up a shield made of hardened air, you conjure a boulder right in front of you to deflect the bullets flying at you. Mechanically, there doesn't have to be a difference at all. It doesn't have to be much more complex than this, if you don't want it to be.
The downside could be that since your magic is constantly ripping things from the nevernever, it is weakening the border between the worlds. Things could be following your character around, waiting for an opening. Or beings are simply dragged along when you rip things through the veil between the world. Like the fire-salamander that clings to the boulder.
If you want to conjure more substantial objects. Evothaum is probably the way to go. We've got quite a few "self sponsored magic" options in the resource section, and if conjuring is not among them, I'm sure we can throw one together. They are basically used to represent a high level of specialization by a wizard, but they require evocation and thaumaturgy to be taken.
You could go for greater glamors as well. The things you create there are as real as it gets and should be enough to deal with a lot of beings. Problem is, that they don't require any casting stress, which might make them a bit too powerful when used in this manner.