Kreel are difficult for another reason as well, they generally have terrible starts to the galaxy. It is almost guaranteed that the starting habs for a Kreel player will be very sub-par and therefore lead to a slower expansion and smaller economy than most other players. However as the game progresses this disadvantage is recovered from, especially if one gains active and helpful allies.
Researching for Kreel is fairly simple. Stealth becomes the focus of the research as the main fleet for the Kreel is a small swarming stealthship. Kreel can also use capital and ship of the line hulls, but this would neglect their main advantage. Therefore concentrate on Stealth, Engines and Hull research topics as these are the most important parts of the ship design.
Stealth Technology to 5
Production to 2
Economics to 5
Production to 5
Ore Mining to 5
Economics to 9
Nanotech to 6
Ore Mining to 10
Production to 10
Military Techs to 5
Stealth Technology to 10
Research to 15
Military Techs to 10
Stealth Technology to 15
Economics to 10
Ore Mining to 15
Production to 15
Research to 20
Stealth Technology to 25
Military Techs to 15
Nanotech to 12
Sensors to 15
Ore Mining to 20
Production to 20
Economics to 15
Have no doubt, this is not a standalone fleet. Toe-to-toe with a fleet of equal resources that is composed of larger ships this fleet will lose due to its low damage output. This fleet is a support fleet, that is its primary role. It is not build for power, but for hit-and-fade attacks and support of an allies capital ships. Therefore all four members of the alliance cannot follow the same ships building guidelines, this would spell disaster.
This ship is a heavy frigate with 11 total slots. Two slots of Hull and two slots of engines provide some defense from mines and missle attacks, and one slot for shields as beams will be the worst weapon against these ships, all tech levels at 15. Follow this up with 4 slots of level 15 beams and two slots of level 25 stealth and the ship is complete.