mechanized Space marine, advice on next expansion?

I'm getting close to being able to (hopefully) add another addition to my space marine army. The issue is I don't know what to add.

Currently I have a captain, a librarian, Two tactical squads, a scout sniper squad, a dreadnought with a assault and twinlink auto, an Ironclad dread, two rhinos, a predator magnetized, an assault squad, a landraider crusader/Redeemer, half a legion of the damned squad, and a devistater squad that can either run four missiles or two heavy bolters and two lascannons.

I've been buggered once with reserves so the favored tactic is to start everything on the board and move up the board attacking as I go, using the rhinos for speed and for 'flat out sight blocking shenanigans, not original but I just started out.

As stated, I don't know what to add next, part of me says throw in another tactical squad with a rhino in since three is a harder number then two to stop, but another part of me says a to get either an elite choice like sterngaurd, vanguard or another dreadnought (Terminators, don't really impress me), on the other hand heavy support choices like the Vindicator or another predator also look intriguing, fast attack land speeders look a bit too flimsy, cept the typhoon variant since distance is your friend. Airpower also looks nice, but again reserves have buggered me over before, plus I'm not sure if a storm talon or raven is better then other choices. I've also toyed with the idea of getting a scout squad with shotguns to act as a assault unit since I only have one other unit with that role and shotguns are 'fluffy' for my chapter.

since I so rarely am able to add units to the army I would like some advice on what I should add since I'm not sure what I actually want and what would mesh best with what I already have.

Thanks for the advice mates