You're welcome :)
If interested I'd like to give you some suggestions (i'd pick one of them, but you could try a mix n' match and see how it works out):
-Have one Holo helper to spawn if you don't die in the first 5 to 10 seconds. Maybe one near the start could suffice in let's say the first 10 seconds.
-A single time upgrade (can be bought only once) that's a bit more expensive than the rest but grants you one Holo helper on level's start. Or cheaper but you need to buy it on every level if you wanted it.
-The rate of spawn modified so it ramps up over time. Let's say the spawn speed/rate for level 5 is 5 units. Make it so it increases over time from 2-(LevelIndex) so in this case it'd start at 3 and speeds up to 5.
I hope these help, cheers :)