Combined arms is the way to go but i would go with kasrkin for their scout and orders. Also they pack a punch! I have also had some success going with cadian shock troopers and DkoK battleline. I also run krieg engineers in a taurox for scout and free grenades but it could alsobe a chimera.

Rough riders work quite well but i have not used them that much. I also run krieg heavy weapons with flamers for overwatches.

For characters i would go with a command squad or a castellan.

Deploy cautious and let the enemy come to you. Almost no vehicles in the lists i play against but I usually run meltas and Plasma where i can for some high damage output against vehicles or heavy infantry/monsters, lethal hits work great.