I want to buy different types of alt coins and not just one.
I will use half for short term trading and other half as long term investment.
What will the value of this 300 USD become in 2020 ?
Thanks for your time and replies.
Have a good day

Great question and everyone will have a different one. First off, have the majority of your investment in Bitcoin because that's the only reason Altcoins are alive today and Bitcoin even though risky, is a lot less risky then alts, but alts have potential besides the fact most are pump and dump.
For me, after going through many alts over the past year, I would say WAVES, Stratis, Lisk, NEM, VeriCoin, Boolberry, Decred, NXT which includes Ardor as an asset, all these coins have something to offer, granted some will fail, some could be where Ethereum was and continue to grow, but the biggest thing is what the coin can offer, that means from the wallet to the community, to the features of the project, read the whitepaper, do research, read the forums, study up on the coins before you put any money into it, and do realize Alt coins are like penny stocks, as fast as they rise, they fall. Best of luck.