Plan 1: Buy BTC and ETH only. Spend $50 and buy 50% BTC and 50% ETH. No schedule and buy on dips.
Plan 2: Buy BTC, ETH, and LTC. Weekly, regardless of the current cost of each coin. Alternate between coins so 1 week buy 50/50 BTC and ETH. Next week buy 100% LTC. Next week buys 50/50 again.
HODL both obviously.
Also at what point is a hardware wallet required?
I think Plan 2 seems better. I always recommend investing in Bitcoin and Ethereum. But you could give a chance for Litecoin also as its price is also giving good signals for the future I think.
But if I were you, I would prefer BNB rather than Litecoin. It has a bigger potential I think and I wouldn't be surprised if its price reaches 1k in this year.