I was gold/plat before the reset. Sort of burned out on it now. Haven't really played that much or well the last few games.
I play random, so I play all races. My favorite combos/builds are (after scouting of course)
Marines/siege tanks/medvacs + upgrades
speedlots, stalkers, immortals, phoenix
speedlings, hyrdas, banes, ultras
I typically send a scout out almost immediately and hide them someone near the enemies base. Then around the 3 minute mark I queue up like 500 Click moves around the base patrolling everything. So I can see what they are building. I also like to pump out basic troops fast, so I can push at the 5 to 6 minute mark if I have to.
I just love marines with siege tanks. I love baiting my enemy in, or dropping them with medvacs. Siege tanks make great defense too. Also, always build detection. If you don't have detection I will have ghosts, roaches, or dark templars in your base asap. That is one thing I always scout, is if they have detection. I also always get up detection as fast as possible. If I am playing a team game with or as protoss I will make lots of observers and send them with my allies.