Welcome back, looks to me you're moving up nicely. I'll say your on a good start, nothing really wrong here that I can see.
Let's see.. your first guy is quite nice.
1st. The only thing you might want to consider on line art is possibly adding in more lines to show cloth folds; instead of trying to directly color them in. Since, your trying to color them in with no lines that's quite the advanced blending method and that's pretty tricky if you're trying to reach that right away. I think most that do that style will usually keep there lines very fine thin/crisp and erase them later completely.
I'd just suggest you stray away from doing that for now.. Since, you're going to need a real keen eye and fine hand to pull that off as your trying to build lines from ground up and add more depth. If your unable, the colors might seem to slur togeather and you'll lose focus on parts against those that are lined. (even if you stick to cells)
2nd. Your flat cell layout is ok so far, you should take it a few steps further in adding some highlights. When you do that your picture really starts to come alive and take shape.
Hmm.. now on your other drawing.
1st. Her eyes now you could add a light source glare seems you have been lacking this a bit. This just shows a bit of gleam to the eyes so they are softer.
2nd. The line cloth folds by her waist could be better. If you got a person with a tight fit try to show more of a stretch pull from were they come as the cloth pinches. By that I mean from where you want to show them start with a semi-narrow path and make them more outward I think that will give you what you were looking to get. Also, if possible try to keep the folds in contour to the body so don't make them so direct or just in one stroke.
That fold on her waist the one above the other should be slightly smaller since it's up higher and showing the first indication of stretch/slack. I advise when trying to show difference of were cloth folds are it's usually good to show some slight overhang from the body/fabric.
(just try to avoid drawing directly inside areas)
Specially that helps to really show off anything that is tight on a female.
3rd. I think her thighs are a bit too wide just slightly since her age. It would be nice if you changed the outer lines on her thighs and brought them in a touch. She is a bit young I find her hips are too shaped from her overall appearance.
Finally.. I like how you have the clothes a bit sharp on the ends but I think you should consider making the inner lines a bit more leaner on the skirt/ribbon.
I hope that helps you some, good stuff. Keep it up looking to see what you can pull out next.