Trying to use what you already have while adding units to make your list more killy or "competitive", I came up with these lists.
Dakka Grinda 1000
HQ: 105
Big Mek: Kustom Force Field; Burna
Elite: 120
Lootas x 8
Troops: 495
Slugga Boyz x 30: Nob w/PK&BP
Shoota Boyz x 30: Nob w/PK&BP
Gretchin x 16: Runtherd
Heavy Support: 280
Killer Kans x 2: Grotzookas (x2)
Killer Kans x 2: Grotzookas (x2)
Killer Kans x 2: Rokkit Launcha
Total Cost: 1000
Orky Rippa 1500
HQ: 205
Warboss: 'Eavy Armour;Attack Squig; Cybork Body; Power Klaw; Shoota/Skorcha Kombi-weapon
Big Mek: Kustom Force Field
Troops: 724
Shoota Boyz x 30: Nob w/PK&BP
Shoota Boyz x 30: Nob w/PK&BP
Slugga Boyz x 30: Nob w/PK&BP
Gretchin x 18: Runtherd
Fast Attack: 135
Deffkoptas x 1: TL Rokkit Launcha
Deffkoptas x 1: TL Rokkit Launcha
Deffkoptas x 1: TL Rokkit Launcha
Heavy Support: 435
Killer Kans x 3: Rokkit Launcha (x3)
Killer Kans x 3: Rokkit Launcha (x3)
Killer Kans x 3: Grotzookas (x3)
Total Cost: 1499
In the 2nd list you could substitute Lootas for the Deffkoptas.
OBGOG