They can be. It's nice to have a $1 option for those who want to support you but don't feel comfortable doing so at a higher level. You don't have to offer anything for a tier. You can label it as a tip jar/purely for support and save rewards for higher tiers. Generally for lower tiers you should otherwise stick with rewards that are easy to create or you are already creating. So this might be a look at WIPs of art or comics, early access to art you already make, etc etc.
You can just make one tier and have it say tip jar or TBD. I'd suggest not over thinking! When you're ready you can go back and refine things. Just make it clear the page itself is a work in progress and it's no big deal. (and who knows, maybe someone will support you anyway, people can be funny like that)