I stopped playing not due to achievements, but because of balance issues and bugs. Don't like to waste my time - I'd rather wait till patch and then will start new game.
Hehe I think you misread my post, mate! I very very intentionally play in a way that will never ever get me any achievements.You have to play the games in Ironman mode to get the achievements.
I suggest doing a large to huge galaxy with no advanced ai empires. This gives you the best chance in acquiring large enough fleets to survive multiple defensive wars and galactic crisises.
For your first Ironman play through, you may want have no fallen empires or just one.
Achivements are listed in the Steam Stellaris profile.