First let me welcome you to the best Ork forum on the WWW. I invite you to join the Way of The Waagh. Just go to THIS LINK
and post a reply that you would like to join.
Now on to your list building. I am a certified card carrying member of the Kult (Kult of Speed) and am more than willing to be a proselytizer.
I recommend a "core" of four to six truck loads of boys. Each unit of 12 truck boys should have a nob with power klaw and boss pole. When assaulting enemy units always try to have two units assault simultaneously, unless it is a small unit that the orks outnumber and can beat up easily (like scouts). Do not waste points on grenades, as with the low initiative of orks you are usually swinging last anyway. Now the argument of slugga vs shoota, slugga boys have an extra attack over the shoota boys, but the shoota boys have better range and twice the amount of shooting. Sure you can only snap fire if the truck moves too far, but it is a minor loss of ballistic skill so go for it.
The trucks they ride in should have red paint, reinforced ram, and boarding plank. The boarding plank is great for attacking vehicles without having to dismount, especially enemy walkers who do not get to strike back (see the FAQ). This one trick brings out much rule looking upping and mewling, especially from blood angel players with death company dreads, really good stuff!
The ram is so you can go through terrain instead of around it, and in the event you have an empty truck with nothing better to do, it can tank shock/ram, although this is usually suicidal it is great fun to ram a land raider and cause damage. The red paint gives you that extra inch of movement, this will allow you to move almost clear across the table (with flat out move that also adds an inch) in one turn.
There is a disagreement that with the new edition that rockit buggies are less valuable, but I find that the twin link rockit is still effective, and with the new edition allowing you to leave disable buggies behind you no longer have to worry about the loss of shooting effectiveness. So I highly recommend at least a squad of three.
Tank Bustas are good this edition, I recommend a full size unit of them. Fifteen rockits even snap firing will shoot down most flyers, and stand a good chance of glancing to death land raiders and monoliths. Their tank busta bombs are good stuff, read the codex and you will see they are some mighty effective weapons, good for blowing up everything armor.
My favorite unit is the burna boys. See The Burna Boy Tactica: This Link
Now on to the battle wagons for the tank bustas and burna boys. I use four rockits, death rollas, red paint, and grot riggers. The four rockits are going to be snap firing every turn you move (unless you go slow which is anathema to KOS) but it is a minor loss of BS and you still stand a chance of hitting stuff. The death rolla is one of the best anti armor devices the orks have, often ramming and killing land raiders easily, not to mention going through rhinos and other such light armor. They are great for taking out walkers as dreads cannot death or glory. On the turns your not ramming stuff, you are moving your BWs to get great position for your tank bustas or burna boys.
Now on to flyers, some here love the dakka jet, however mine must be cursed as it has yet to do any real damage to the enemy and usually gets shot down the turn it comes on the board. However, I have had some good results with the burna bomma, take four to six of the missiles depending on your points, and make those lonely fiery bombing runs, good stuff. I could tell you all the good stuff my burna bomma has done but would probably hit the character limit of this post.
Another favorite of mine is the Green Baron. For a detailed tactica on the green baron go HERE
While a suicide unit, it does enough damage from time to time to keep him in my list. Sure some games he gives my opponent a VP with no return, and other games he gets behind those pesky IG big gun tanks and takes out the squadron or keeps them from pounding on my others units as they zoom across the board.
Lastly but not least is my HQ. Now, I only use the big mek with KFF as mentioned in the burna boy tactica. Cheaper than most other armies HQs and a bit more expendable. I run him with the burna boys and if/when they get into combat he accepts any uber character challenges so that the burna boys can shred the unit that they are stuck in with. Not to mention that NOBODY in their sane mind charges a burna boy unit. If they do, they only do it once and then cry cheese.
I hope I have attracted you a bit towards the KOS side. As a side note and warning: Orks are addictive! Once you start you will be hooked, and the longer you play them the harder it is to break away. A sure sign of the addiction is OIADD (ork induced attention deficit disorder) where you will be thinking of ork lists at work, new models when driving, painting boys when you should be mowing the lawn, inventing new tactics while trying to go to sleep, and so on. So run away now, or be prepared to become addicted.
If you hang around here long enough you will soon learn the good things of life: To krump your enemy, to see them flee before you, and hear the lamentations of their players.