What is the best thing to invest 30 to 50 thousand dollars?

Unless I had a mutli-million dollar portfolio I wouldn't dream of starting a new position with that much.  No investment is a sure thing, I remember watching an interview with famed investor Peter Lynch from the 90s and every company he mentioned except Dunkin Donuts is gone (he mentioned Fannie Mae which isn't gone but the government is seizing all its profits for a decade now). 

While waiting for Joe Biden and the Democrats to really mess up the economy, I am tending more towards ETF's and Mutual Funds. And I will be putting tight stop losses on the the ETF's. 

As to a specific investment? I don't give investment advise since Your objectives are not MY objectives. 

I really doubt you have much more than $10.  Anyway.  You would put every dime in a Roth IRA that lets you invest all of it in the S&P500 where it will give you a net return of +12.5% per year for every year you live.

The best thing you can do with that money is put it all in VTSAX, and let it sit for a minimum of 30 years.

real estate .........

Consider looking into ETF's for a start. Thoroughly investigate the ones you are looking to invest your hard earned money. 

It's up to you to do your own research. I would go hunt for value stocks with low P/E ratio, good margins, reasonable debt levels, good management, and high net assets relative to share price. 

I would put $5000 in a low fee s&p 500 index fund and then $1000 a month. If we have a big market decline, consider adding another $5000 and upping it to $1500 a month and continue until its all invested.

Warren Buffett called an S&P 500 index fund “the best thing” for most people who want to invest. ... For years, the so-called Oracle of Omaha has championed index funds. 

Invest in a phone call to a financial advisor.

For that much, one might actually call you back.