Heres what I did man, and it got me 4000pts of Orks for like $400 NZD (so think 20% of retail or so)
Buy a buckload of boys online, and another bucketload of bits. You'll often find Assault on Black Reach Ork sets for dirt cheap, so snatch them up. Then just build them into everything you need - I've made Stormboys, Kommandos, Lootas, Burna Boys, Nob Bikers, and Battlewagons (using dollar store tanks and random bits) - everything is very cheap and get complemented by other players for being more unique and often better looking than the
GW models.
As for the list, you've got a few things right but that other stuff sort of betrays how new you are to Orks. Scratch the Wagon (Wagons are good, just not for you) and the Kommandos (rubbish) and go for what I call the "Lootas and Shootas" list.
Shoota Boys xheaps
Lootas x20-45
KFF Mek w/ Ammo Runt, Cybork
And Optionally
SAG Mek w/ Ammo Runt, Bosspole, Cybork *or* another KFF Mek
Dakkajets
Aegis Defense Line w/ Quad Gun/Lascannon *and* Big Gun Lobbas.
Heres a 1500 point list for you using the above selection;
2x Big Mek w/ KFF, Cybork, Bosspole
30x Lootas (two mobs of 15)
112x Shoota Boys (mobs of 20 for mobility, as large mobs can be hard to maneuver, or 30 for efficiency, as large mobs are stronger than same # of boys in smaller mobs due to Mob Rule. No Nobs.)
Aegis Defense Line w/ Lascannon
Big Gun Lobbas w/ 3 extra krew, 3 ammo runts
=1500 on the dot
Divide force into "Lootas" (a gunline of Lootas,
KFF Mek, Aegis and Lobbas) and "Shootas" (Shoota boys,
KFF Mek). The former sits back and shoots, the latter charges up the map and snags objectives. Use the BS3 lascannon against Armour 14 as its the most reliable long ranged anti-tank in the entire Ork codex. Lobbas bomb anything soft and clustered together - honestly, consider these just "free shots", the main reason you get this unit is for BS3 on the lascannon, and make sure to liberally use those ammo runt re-rolls. Lootas sit in cover (put some behind the Aegis if there is room) and dakka the crap out of everything that isn't Armour 14, including air. Make sure that
KFF Mek at the back is attached to a Loota Mob (they have terrible morale, bosspole the living daylights out of them if they start to run) and gives cover to everyone who cannot otherwise get it.
Remember three key things
>Only one model from any given Ork mob has to be within 6" of the Mek to get
KFF for the whole mob
>Grots from Lobbas can fire the Lascannon at BS3 instead of BS2 like the rest of the army
>Grots cannot see over the Aegis, but also cannot be seen most of the time in return! They're practically invulnerable if you do this right. Lobbas can nuke stuff as long as something else can give line of sight to it. Put the Lascannon on the edge of the Aegis so a Grot can use it and still see.