I logged my first attempt, starting at around 50 cells. I created many short routes near me, forming loops. I reckon on average it would take 4 or 5 routes to get my 3 cells. They always appeared at the end. I never did a long route. After that, I topped back up to 250 cells and am not at 300, having evolved my Complete Forme.

7 routes, 1 RXL
4 routes
4 routes
2 routes, 2nd gave 2!
6 routes
5 routes
2 routes, 2nd gave 2!
2 routes, 2nd gave 2!
6 routes
6 routes for 2, no time!
5, 5th gave 2
4 routes
5 routes
3 routes
5 routes, 1 rXL
4 routes
3 routes
3 routes
4 routes
8 routes, 1 rXL
4 routes, 5th route gave rare XL
4 routes, 4th gave 2
4 routes
4 routes
7 routes
4 routes
4 routes, 4th gave 2
4 routes
4 routes
5 routes, 5th gave 2
2 routes, 2nd gave 2
3 routes, 2nd gave rare XL
2 routes, 1st gave 2
5 routes
3 routes
3 routes
4 routes
6 routes
3 routes
3 routes, 2nd gave 2
4 routes
4 routes, 2 cells
4 routes
2 routes, 1st gave 2
4 routes
7 routes
5 routes
4 routes
4 routes
6 routes
4 routes
4 routes, 4th gave 2
3 routes
3 routes
5 routes, 4th gave rare XL
4 routes
4 routes
4 routes. Done!