No. 37 is one of the easy left hand etudes, 12, 41 are also fun. No. 8 is probably a harder left hand etude and No. 23 felt awkward for me.
No. 10 is the easier double note etude. I tried No. 34 after I did No. 10 and No. 39 looks cool. No. 30 looks difficult.
No. 31 deals with thump crossing.
No. 50 was the first one I learned but its probably one of the hardest but it didn't scare me away. Others are more difficult for me.
No. 1 and 2 are pretty easy also.
No. 18 deals with crossing the hands.
No. 40 is probably easy. I heard someone say it was lol.
I would pick an etude that helps you with some kind of technique that you want to improve. I played 37,12,41 to get my left hand better and No. 10 for double notes. I learned No. 50 because it sounded good.