First of all the MS Elise it the car for this series.
You don't have to max it out. But, a Level 2 turbo, with all the suspension and tranny mods should be enough. Get a set of T2's or T3's. Run the T2's on back and T3's on front. The Elise tends to be hard on rear tires. The harder tires in the back will even things out.
Then qualify for each race. You can then find out if you have the tranny adjusted to meet the needs of the track. You want the gearing to be short enough to run near the top of sixth gear on the longer straights.
Lastly, drive as smoothly as possible. You won't be able to muscle them around, or push them out of the way. So smooth will equal quick.
Also, with the T2's and T3's, if you drive smoothly, you may not have to pit at all.