Most altcoins follow the trend of Bitcoin, and so it's very likely whatever happens to Bitcoin has got a reflective effect on them. So I would prefer to buy at this moment because by that time, the trends must have gone far and you will not be able to buy at a good price or FOMO may set in and you may take irrational decision that may not be a good financial decisions. If you buy now before the halving, after the halving, by the next bull run, you may be able to get some good profit on your investment.
Buying during halving isn't a bad idea but then it could be buying at a bad price because definitely their will be volatility due to demand resting from the halving.
Few do not follow the Bitcoin trend depending on the hype and currently, Solana is looking good. It has already crossed the $100 mark and if goes on like the way it has been then it will hit $500 after halving. There is another cryptocurrency that has been performing similarly and it is AVAX. At the moment it is moving upward steadily, by next year it should be near $100 and after halving I think it would break its ATH.