Yep, belongs in strats really.
But, while I'm here, my advice is to watch some super play videos to see what is
possible. Being a mere mortal myself, I usually manage 50-60M on level 1 and ~120M after level 2 (can't remember the rest).
To score really high you have to exploit the close proximity 'gem leeching' technique - see the strats here and at cave-stg.com (now open to guests

) for more details as well as watching super plays. The technique is high risk though and takes a lot of memorisation - I only fully exploit it on level 1.