If you have a lot of capital then I suggest go for bitcoin since its considered as the most volatile currency. It will surely be up again back to 16-17K. But if your low on budget then go for ADA,ETH,XRP.
"Low on budge" - he doesn't need to buy whole bitcoin..... he can buy parts of it
Nobody knows answer to your question, I will be happy if I knew and I'd pick the best one out there :/
I really wonder if your too ignorant enough or just totally newbie in this business. As you can see bitcoin is considered as an unpractical option right now. You know what? Because if you are in "low budget" your investment would just totally go to the transaction fees. Hence, instead of profiting you will end up losing. Understand?