First of all let me tell you this not the best angle for a critique picture. Either a angle looking directly down on the nail, sideways or down the barrel, but preferably all of them. Also there is a bit of excess of cuticle oil, this makes it very hard to tell if your work is nice an tidy around the cuticles, or if it is touching the skin etc.
Now for my critique. The first thing that drew my attention was the color, specially the free edge, it is very grey and unatural, looks stained and so not very flatering. The nail bed color is also a bit off, too pink in my opinion.
It is hard to tell the shape of the nails due to the angle of the picture, but they are unconsistent and i would say they lack a shape, they are neither square, squoval, round or oval. Try selecting a shape, see what are the caracteristics of that shape and try to stick with it on ALL nails.
Apex and product placement is very hard to tell, again due to the angle of the picture, but as you said, the thumb if off, and the rest look a bit too thick of the free edge. A natural looking, balanced nail should be thin of free edge, sidewalls and around the cuticle and thicker over the stress area. To determine exactly where this is press downwards on the free edge of the nail. See that part of the nail becoming withish? That is the stress area...
Overall, hope i wasn't too harsh... After all i did do terrible nails when i started off. Congrats to you for posting, hope you pick up on the flaws. After all, it is a learning curve