I know some people say usually they just stick to one thing once they've started using it. One thing I've found is
1.) Using potion 5 blue 100 Red 100 Yellow - this potion emits the green gas continuously for at least 10 seconds. This can be useful if you throw 1 or 2 of these when the spiders start coming while throwing the yellow blob
2.) The yellow blob doesn't have to be expensive plus it is very effective. With variation 5,5,7 it is enough to stick and destroy the enemy.
3.) If there's too much overwhelming you, make the red rocks that explode 100 blue, 0 Red, 100 Yellow
Great game - although there should be more ways for defense.