crossing sets?
could i have something like a wolver helmet with a cobalt chestplate and cross two sets of gear so that i can increase the variety of damage types im resistant to? or does that not work out well?

Yes, you can mix sets. Actually this is very common. For example, Perfect Mask of Seerus is a very good helmet with no matching suit. So players pair it with Shadowsun, Chaos, etc.
As Traevelliath said, you will eventually want specialized sets. But in my opinion it's more important to protect against status than damage. Try to get a shock set, a freeze set, and a fire set. Until then, you can pair shock with fire (for example) to get a little protection against both.
As Traevelliath said, Cobalt armor is some of the worst in the game. So don't pair it with anything. Yes, I know that the recipes are free. It's still not worth it. Just get truly good armor instead.
You seem to be interested in swords. So you might read the armor section of my sword guide. Actually Traevelliath has repeatedly pointed you to it in another thread already. Now is the time to read it perhaps.

Cobalt has very little use...... best leave it at 4 star till you can upgrade it to the Almirian Crusader set (which is hard to get).
It also could have some use if you get Max UVs in Poison, Normal, and Pierce...... but that is really ONLY for swarm levels in which the only reliable sources of damage income are Poison slimes and Normal damage bullets.
yeah ive read through it a lot, helped me determine the pros and cons of some swords i was contemplating whether or not i should spend crowns and resources on.
I find it's best to have a full set for each damage type. If you don't have that budget, then at least get a shield for each damage type. I don't find mixing defenses to work too well. I'd only recommend it for the status defenses, which can be far more valuable than pierce/shadow/elemental/normal defense.
That said, Cobalt is generally inferior to Wolver in every sense. I wouldn't recommend it.