Mainly just hodl & sell pumps. If I get enough to aquire a second masternode of something I do so (so it compounds). I'm expanding horizontally this year though, want a wide variety, so I'm steadily accumulating my long term holds. I ditched my low price 0 utility mnodes BTW (as in, if it's just a currency, drop it). If it's still profitable and hasn't dropped too far it stays for now.
Bear in mind, they aren't always strictly called a masternode - but really, if you have a set amount you need to stake, and have to assist in the operation of the network in some way, it's basically still a masternode in my book. Link is an example of that. Obviously stuff like Link hasn't launched yet, so nows the time to accumulate (yeah, yeah, Link is a meme etc).
So in no particular order here's a sample:
Mirq, Weycoin, Ark, Btc Green, Colx, Dero, Loom, Payfair, Substratum, Stratis, Sia, Chainlink, Sigma, Graft, REBL and my new favorite Xuma.
Obviously not all running yet - so I'm stocking up now. I'm forgetting quite a few though lol. I have a whole spreadsheet of em. Just dropped Stipend and a few others that are decent earners, but have no future. I'm considering getting into Blockstream - it's kinda, sorta the same boat (you vote on property listing etc to get rewards). Basically, a masternode should require you as an active, necessary partner in the success of the network. If they say it's free money, it's a scam. I mean, some like Weycoin are still scams haha, but they require more than just a stake.
Protip: Xuma. Dyor of course. But Holy fuck, potential plus. Decentralised NoSQL database, right now Dapps need to use a regular DB. If Substratum is providing the hosting, Xuma will be the DB. Cheap as fuck too, and I never see it mentioned.