5k is a good enough amount to start. Crypto is a really risk space and you should never invest more than you can afford to lose. Instead of asking which cryptocurrency I should invest in, I'll suggest you to do your own research and understand how cryptocurrency market works. Cryptos are extremely volatile, it's not uncommon to see 40–50% profit or loss in a day.
Depending on your personal risk appetite and rewards expectations, you can look at different coins to invest in. If you are looking for small gains with minimal risks, Litecoin, Ethereum, Ripple are pretty good coins with proven tech. I can assure you if you hold these coins for a year, you can easily look at atleast 3x gains(conservative numbers).
In case you want to multiply your money rapidly, I'll suggest start researching small cap coins, they can grow 5–10x within matter of days but do note they're all speculation based and 95% of them are shit coins which would eventually go to 0. If you are able to identify a good coin and enter at the right time, it can help you grow your capital by a lot. One of my personal favourite is XRB(Raiblocks), it's a pretty new coin with promising tech backed by a great founder. It's the fastest payment coin out there, can handle 7k transactions per second. Still I'll suggest don't take my word for it, open their reddit sub and do your own research.
Also, start learning technical analysis and follow https://cryptopanic.com and reddit subs of your coin closely. Feel free to ping me personally if you need any help.