RE: Which one of these can make you rich if you buy now?

I don’t know if they’re going to make you rich. In crypto, there can be made predictions, but they're nothing more than calculated tisks.

I agree with @bruizer that you should do your own research and that it is safer to spread your investments than to bet everything on one horse.

A couple of days ago I wrote a post (you can find it in my blog) about why Cardano and Stellar have a good chance to grow ‘Ripple-style’.
Recently, Stellar made a deal with IBM which could turn out as a golden combination.
Cardano is still young, but has big plans for the future. They’ve already proved that the team behind it is pretty smart by choosing Japan as their launchpad. Plus, it’s even faster than Ethereum and is building a platform that will support both Bitcoin and Ethereum Classic.
Both have seen a huge rise in price (+1000%) since December and they may keep this trend for a while.
(You can read the entire post with more info on my blog)
But again: in crypto, everything is possible. Something what’s goin up today, can crash tomorrow. Only invest what you can afford to lose.
Can’t say anything about Sia. I’ve read loads of promising information and wanted to buy some, but for some Reason I don’t remember, it simply didn’t work and I ended up completely confused. That’s when I decided it’s probably not the coin for me :-D