I casually buy and sell domains. Used to do it heavily when I was in college but have turned down my investments in this space since I believe it is fundamentally antithetical to a free and open internet. I'm usually happy to let go of my domains for substantially lower profits if someone has a genuine need.
This is just to qualify my next statements.
Domainers grossly overestimate the impact of domain names. Entrepreneurs grossly underestimate it.
The truth is somewhere in between. Domains are important, but they're not going to make or break a shoddy product.
As long as you get a domain that's pronounceable, easy to type in, and memorable, you should be fine.
In particular, this means staying away from exotic extensions - both gTLDs like ".travel" and ccTLDs like ".io"
Because the average user still thinks of the web as .com. Tell them that your website is abccorp.io and they will type in abccorp.com. In fact there is a cottage industry of domainers who buy .com versions of websites in other TLDs just to make money off the type-in traffic.
If you can't get the domain you want, add a prefix like "get"
Remember that domains are essentially about branding. You want to sound familiar yet stand out. Imagine the domain name as a standalone retail store. Does the name make sense? Does it seem trustable?
Like if you're selling watches, "WatchCenter.com" makes sense. You can practically imagine a big retail chain named 'Watch Center'.
Some of favorite prefixes/suffixes to get solid brands are: hub, mojo, hero, smart, open, start, center, station, base, next, genius, zap, wire, active, metrics, dojo.
Add them before/after a keyword to get a decent domain (like "InstaPayments" or "CodingDojo.com")
Just make sure that you stick to .com