First, kill the idea that a bull run will happen during the halving. It could, but just leave it at a high probability. For altcoin to DCA, how about you simply go for Ethereum or BNB? I find these two altcoins to be reputable and worthy of hodling. You may want to add Solona, Ripple, or even Doge which is a meme coin, moreover, I advise that you diversify your portfolio and hodl a fair number of altcoins so you don't feel stuck or tied to one particular altcoin. DYOR too, It's only my opinion I'm dropping.
true, halving might not be the reason the market will be having bullrun, and its not like the market will instantly become bullrun when halving arrives anyway, its the ETF news that has been changing the market for the better and make it go in the direction of bullrun. therefore having too high expectation and thinking that that we can make profit out of that event would be wrong I guess.
regardless I also don't recommend investing in BNB as of now too much problem has been going on with thisn platform, moreover they have decided to close off their service in the US this simply means they don't have access to the large capital of the US that can help the exchange thrive, which means might be a sign of BNB hardly increase because the exchange volume might tremendously getting lower.