The risk of a margin call depends on the leverage on margin and the volatility of your account (not of a particular item in your account; usually every equity in your account counts as margin; it depends on the brokerage's assessment of the likelihood that the equity will tank, especially if it's an illiquid or penny stock where the volatility can go sky-high if a squirrel farts in the park).
So you can use quality equities as margin to borrow to buy volatile equity, even if the equity you buy isn't marginable.
When you buy, generally you have to have at least 50% margin, but after that you only have to maintain 30% margin. If the volatile equity is only a small part of your portfolio, you'll start well above 50% and stay well above 30%.
Putting every dime you have, and doubling-up on margin, into something that's likely to drop 33% in a day is not wise. And as I said your broker will probably be on top of that and not allow you to use the first tranch as margin for the second.