Yes, don't buy for a while. Learn, research, follow sales, learn about extensions...
My personal advice is :
Stick with .com ( at least to begin with ) and/or with your cctld if you know the market.
If you have a field of expertise go with that
Avoid dashes and numbers ( yes...there are exceptions )
Register something THAT MAKES SENSE
DON'T put name for appraisals here on NP or you will soon find out how nice the pros are...
When you feel ready GO FOR IT! Follow your intuition.
With that $100. Don't buy 50 domains with $1.99 coupons. Buy 1 domain in the domain aftermarket (say with a drop-catcher), and sell that for $500. Or maximum of 2 domains. Buying a load of crap domains with your $1.99 coupons isn't spreading your risk.
I COMPLETELY DISAGREE
We, as domainers, are investors. Who would be so stupid to put ALL his money in ONE name? Would you invest all your money in ONE STOCK? No way.
I have been investing people's money for years and spreading your risk is rule number one.
If you have 100$ as a budget my advice ( after you studied and learned ) is :
Buy 2-3 closeout domains ( please try to buy some good ones... )
Hand register 20-30 domains ( hand pick them carefully ) possibly with coupons.
Don't rush, take your time
Be happy if you make 1$ profit ( aka don't be greedy )
Here you can find some interesting stories
https://www.namepros.com/threads/your-hand-regd-dropped-domains-success-stories.842433/