Advice, tips please

I have 7 seedlings that are a couple weeks old in styrofoam cups, 100% potting soil with holes poked in the bottom, no ferts and i water thoroughly then wait a while(few days) until they're as light as they were when they were dry, then I repeat. I am planning on transplanting soon into 1 gallon pots with a perlite/rich compost mixture. I will be finishing in 3 gallon pots so I must transplant again and perlite always seems to make the soil very shaky and loose, hard to stay in a clump. So,

What amount of perlite do you recommend putting in these pots to have adequate drainage and still have a tight enough mix to avoid everything falling apart when I pull the babies out to put in their final 3 gallon pots?

any advice appreciated :)

I will probably take clones as well after i determine sex.