Some people are newbies and do not know anything about certain scams. I remembered when I started in crypto world, I visited a certain site, I view ads and I am paid 22 satoshi or less, I viewed an ad and it was about mining and I was offered to pay 0.2 satoshi to get 0.5 satoshi. The offer was too fake to be real and I did not do it.
Some people will be attracted to it and would just be scammed because people just like double offers.

I will suggest you to buy doge or digibyte. And, know one thing for certain, low marketcap coins increase prices faster than high marketcap coins. So, with what said, know when to sell this coins if bull market is over.

This depends on how the market is. The only fiat that is profitable to buy is dollar because you can convert cryptocurrencies to dollar at a very low charges on exchanges. So, it is like converting to cryptocurrency.

During bull run, people buy altcoins, that is why altcoin price increase could be double of bitcoin, so it is good to convert from bitcoin to altcoin at the time.

If bearish market begin, people convert back to bitcoin, this is why the price of bitcoin do not decrease like that of altcoin in bearish market because people demand for it.

During bearish market, some people just convert their money to dollar as I said in the beginning and buy again when the price is low.

Aside dollars, I can not advise someone to convert to any other currency except exchanges support the currency and if the currency value is not much decrease like some countries money.

Swing trading is less risky to day trading but with $50, I will advise you to be patient, learn about analyses, try demo and make your risk. In day trading, it is very possible to double it to $100. But, very risky as well.

To invest in first 30 coins means you should invest in first 30 with highest marketcap. This is true to me because although, low market cap coins could be highly profitable in bull market but are also more risky as the losses are more during bearish market.

The best coin to buy in 2020 is Dash. This is not just my favorite coin but it is one of the coin that is really profitable if hodl.

These cryptocurrencies are also food for investment in 2020:
Ripple
Doge

Investing in litecoin, zcash and monero is also not bad.

We should know that low market cap coins are more risky in bearish market and also more profitable bullish market.

Day trading is very risky, although, could be very rewarding and profitable. The market will always be volatile. To minimize the risk, you can try swing trading. I have tried it for over two years now and it is better.

Before the previous in 2016, but market has started and the price of bitcoin increased. So, the tendency that the past would repeat itself is likely but not 100% certain.

But it is certain that holders will not lose but gain profit at later months after halving if at all the bull does not start early. So, what matters most is the bull run to start this year so investors can profit.

US dollar is one of the strongest world currency, it is even the most recognized and that is why stable coin mimic dollar to an extent. Despite this, this can not cripple dollar, not possible this time or in future. Dollar is also and always stronger than any stable coin.