For your first time sprites they're really good. I especially like Traproot and Minnowhite, and think these ones are the best design-wise, and sprite-wise.
The design is simple, yet still gives a Pokemon vibe. Lineart and shading is pretty good.
I would suggest you increase the contrast between shades a little bit to make shades more visible, as well as smoothen the lineart especially with Tarocktula and Titanigon. I also feel Titanigon's scale overlapping is overdone, and can be simplified. Remember, Pokemon designs are simple.
I really like the Aquamoeba sprite though, those highlights really give the sprite a slimy feel and the nucleus and other contents within the ectoplasm brings the sprite to life.
About your concepts, I like Peagarow. Has the design attributes of a Pokemon, though maybe you could add a belly or a pattern to make it more colorful, and less animal like. You might want to play around with the proportions too. Oh and I can't see Tanchor.
Keep practising and you'll sjurely get better. I like what I'm seeing so far, keep it up!