You need to ask yourself on how much you will start cashing out upon investing to BNB. It's also a factor on how long you are willing to hold BNBN.
If your answer is long term and you are willing to hold it, the current price for BNB is good for you to invest. It's under $30 so consider it as sale, may I know on how much you're going to invest?
It should be the amount that OP willingly invest with BNB. We need to understand that BNB is also for a long term investment.
But I think it is good if OP will buy first bitcoin and ethereum before buying binance. However, it is up to us what coin we are interested to buy with. Buying bnb below 30 dollars is much better because if it goes up, there are many profits.