Made $2k in 2 months mining Ethereum. Making much less now that difficulty is skyrocketing. There are also other coins that are profitable (although not nearly as much).
I actually made my entire investment back on the mining rig just day-trading... But I'm done with that for awhile because watching crypto markets 24/7 is a pain in the ass.
As far as AMD's marketshare, it has definitely improved this year, but mining has probably hurt it significantly on the gaming side. There were a lot of guys with "connections" who filled up WAREHOUSES with RX480 rigs. There were pics of these warehouses a mere 1-2 weeks after the 480 launch, just in case you were wondering why stock was shitty for so long!
FYI, my rig had 370s/380s in it for a long time, then I slowly moved it to 5x 480s and 1x 380 as stock of 480s popped up here and there (and for a reasonable price).