Orks can do anything that any other army can do and do it better than they can. However, they cannot do everything that any other army can do. Make sense? If you make an ork assault army, they'll out-assault any other army in
40k. If you make a shooting army, you can outgun
IG or Tau. If you go foot-slogging, or mechanized, or kan-wall....all those options make you a completely awesome army, but there's a catch. You can only do one of them at a time with an army list.
If you combine a mechanized and a foot-slogging list, you're going to lose. If you have part assault, party shooting, you're probably going to lose. Your strength is in being able to pick something and be completely awesome at it. So before giving you advice on where to go next with your army, you need to pick a theme and build around it. If you want a bike army, or a shooting army; an outflanking army, mechanized, assault, figure out what your playstyle is and start building your units and armylist around that idea.
THAT is the strength of Orks.
If you're going to play Kult of Speed, then you want to get into combat as fast as orkishly possible and assault. Drop your rokkits off the trukks, you're not going to do anything with them anyway. Trukks come with a big shoota by default. Take 'Eavy armor off the Nobs as previously mentioned. Want anti-tank? Add boarding planks to your trukks. You've got a mek with a
KFF in the middle keeping your trukks alive, so you'll be fine getting up to the enemy lines, but you shouldn't see a ton of tanks in 1500 points. Kommandos honestly should be 15 or none. Snikrot's boyz strike at I3 even on the charge, and so are going to get administered a beating before they attack; they always do. I like Snikrot for his psychological value.
And finally...I willingly a trukk squad or two to get a squad of nobs in a trukk; 10 nobs equipped differently with 'Eavy armor and a painboy; attach Ghazghkull to it, and you've got a beast of a unit that can kill anything including land raiders and monoliths. Ghazghkull on the charge is a terror to behold, and if he's in your army and you play well you can take the bosspoles off the rest of your army. When I play speed freaks, I charge on turn 2 or turn 3, and on the Waaaugh! My entire army is fearless when I do it, and if I lose combat, I take fearless wounds.