Any alt coin suggestion expect ada.In my point of view of ada still can't surpass ETH in the smart contract field and even if they can make it will be hard to be replace existing eth smart contract eco system.Moreover late coming project like sol even surpassing to ada,all things ada have is the loyal user base and nothing special things in tech
Have you tried doing research on WAX, SOLANA or AVA?
I noticed these three crypto tokens really have a bright future. for the long term, still what I recommend is bitcoin, maybe you can be these three as an alternative to your investment besides bitcoin