Buying a coin that you can easily stake or join a shared masternode with.
This is still a gamble, but you are passively earning more of that coin, in hopes of when the price goes up, you have that much more to sell.
For example, SnowGem takes 10,000 XSG as collateral to operate 1 Masternode (MN), current cost = ~$200 per MN. There are 2 ways to earn from a MN, operating a masternode by yourself with purchasing a $5/month VPS (safest option) or joining a shared masternode service like the site evonodes.com (who takes ~20% cut of generated coins and does not supply you with private keys). I have a picture attached of the current stats of SnowGem Masternodes on a site called Asgard showing that it is profiting $7.40 a month - $5 for VPS cost = $2.40 profit, but these are at crazy low XSG/BTC prices, in my opinion.
There are also other coins that are proof of stake where you mine the coins by holding them, which ETH has been trying to become PoS (proof of stake) with Casper 2.0 for the past couple of years...but there are other coins currently operating as a PoS with the same options out there of using a 3rd party website at a slight fee (typically) of the generated coins you get from staking the ones you have on their site.
Just be careful if you are new to the space and hopefully this answers your question even though you probably didn't mean to ask for this type of approach, but the best way I think, outside of GPU mining, to gamble on a lesser known name coin and have them come out with some positive news propelling the coin 100%+.
Always remember, not your keys, not your coins.