Minion Masters

I haven't unlocked this achievement yet (currently at about 180 wins), but I found a method that has really sped things up. That method is to play against people much worst than me. To do this purposely forfeit matches and never win multiple games in a row. Winning consecutive matches gives you more battle rank causing you to play better opponents. Find a rank you can easily dominate, for me it is sliver 2. Then win 1 game (usually takes me less than a minute), and back out of the next to keep your battle rank points about the same (takes 3 seconds + load time). With this method, I have been getting a win and a loss quicker than I could win a game when I was in platinum. Don't use this method in the team modes though, it wouldn't be fair to your partner.

This achievement is for winning 500 ranked battles. Ranked Battles include the following:

1. Solo Ranked
2. Team Ranked
3. Premade Team Ranked

The best way to get this quickly would be to split your time evenly amongst the three game modes. At the end of every season, your rank will be reduced to hopefully allow you to get some more easy wins, however the key to getting this achievement is having a good deck.

Strategies change constantly due to the balancing of existing cards and releasing of new cards and/or Masters and so it would be worth experimenting to see what works for you, or seeing the strategies of better players and trying to mimic those.

This achievement does track on Xbox Achievements (5 wins =1%) and in the in-game achievements to make it easy to see where you are at. Note that the "total wins" you see on your profile includes unranked wins which do not count towards this achievement.