Depends entirely on the game. From the cpu fps output to the gpu fps onscreen, it's all dependent on the game in question.
I run a 3770k @ 4.6GHz. A gtx970 with 128% OC. In Starwars the Old Republic, single player or 8man operation I have 0 issues with taxing the 90fps in-game cap. Bump that to 16man, and I'm turning off cpu bound stuff like name tags, floating damage etc. Just to alleviate cpu limits or the game gets stuttery and laggy. 24man world boss fights are abysmal. There's simply far too much AI from all the other players. I get drops to 5fps and average 15fps. It's all cpu limits, changing detail levels does nothing, the gpu has no problems.
CSGO, I can hit 300 fps in office. Again cpu limited. Minecraft, same thing. Skyrim64 with over 170 2k/4k/8k mods, and HD physX has no issues with well over 60fps. It takes Metal Gear Solid V with a 4k DSR to get the gpu to 99%.
The r9 380 is in no way a bottleneck for the 3770, regardless of what any calculator tells you. In some games you'll be cpu output limited, in other games gpu detail limited.
Depending entirely on which particular game you play.
SSD, best upgrade, just for playability enjoyment, it sucks when the hdd takes so long to load the map that your team is long gone and half dead by the time you drop. It sucks going in/out city's or buildings and waiting 30+ seconds for each map to load, it sucks when starting a multi-player match and get booted from the team because load times are too long and people don't want to wait.
Not all that much difference between a 380 and 390. Not worth the money for a few fps you won't generally see as it's beyond the refresh of the monitor.