That looks awesome for a first mini - God I wish mine'd looked that good!
lol
As for any constructive critque: we are own harshest critics! Edge highlighting is very very hard. One thing you can do, if it still bugs you is go back over it with your base blue colour (that pretty medium blue you have) and 'straighten' up the lighter blue.
I don't know what brushes you have, but while practice is very important, so is a good brush
imo - it helps a lot, especially with edge highlighting
imo. I wouldn't say run out and immediately buy a set of good brushes but a Windsor & Newton series 7, size 0 is really really good for this particular use. And wouldn't be a bad brush at all to have in your arsenal
Also, a couple things to help your model pop a bit, if you want: I might, as mentioned elsewhere, paint the spikes on the helmet metal. All of them not just the tall one. Then I might also do a couple 'scratches' of leadbelcher, with a small silver highlight on the top, to give it a bit of worn look. You can also use a bit of nuln oil maybe over the whole helm to give it a dingier look, which may be more fitting with an Ork. Up to you of course!
one other thing - I might go back over the laces on the back of his pants with a little offwhite, or zandri dust highlight. Or bone or any lighter brown really. If it's too stark when it's dry, hit it with (again) a nuln oil wash (just a little bit, use the tip of a small brush rather than like swamping the area with your wash brush).
And last thing - which is something I love - one of the painters here (sorry I can't recall his name off the top of my head
atm) explained how he painted toofs! He used brown as an underlayer in the whole area, and then painted the teeth per the usual bone method. I'm not saying your teeth are bad!! They're great! but you'd be really surprised how much that brown helps the whole thing blend in and then helps you pick the teeth out. I've been in love with this method since I started using it, it's awesome
And anyway, just in case I sound too critical, don't take it as negative! Just trying to pass on tips and tricks I've learned and honestly that mini is freakin awesome especially for someone just getting back into the hobby!
Have fun and happy painting!