If one is going to borrow to invest, it's always better to take out a separate loan and use the proceeds to buy shares. There are no margin calls that way if the price goes lower. Buying on margin can wipe out your entire investment if the price declines as margin calls force one to sell shares to maintain the required ratio of debt to equity. Non-margin loans leave the investor in control, and unlike margin loans, only result in a total loss if the price goes to zero. Margin loans can result in total investment loss long before zero is reached. No one pumping their margin strategy ever mentions this pitfall.

I don't believe AMBS is allowed to be sold on margin at most U.S. brokers.

The answer to the buying question is YES.