Is it mandatory that I offer rewards or suggested donation amounts? No.
Should I? Maybe. Ask yourself a few questions...
Should I Offer Rewards?
Rewards can be a great way to thank your donors for their contributions. They can be retail items, like coffee mugs, t-shirts, etc. and can also be digital gifts and levels of recognition, for example facebook shoutouts, thank-yous in your annual report, recognition on your website, etc.
Capacity - Do you have rewards to give?
Distribution - Will you offer physical rewards such as t-shirts that you will need to ship to donors? Can you offer rewards that can be distributed digitally?
Fulfillment - What is your capacity to get rewards to donors in a timely manner? Do certain rewards need to be limited to a specific quantity?
Relevance - Why are you offering rewards? Are they items or experiences your donors will actually care about? Do they relate to your mission?
Pricing - How much will it cost for you to acquire and distribute each rewards? Which rewards are most exclusive?
Stacking - Will you offer all rewards at lower tiers to those who donate at higher levels?
Should I List Suggested Donation Amounts?
Unless you have a reason not to, it's advisable to suggest donation amounts. They can be arbitrary if you want ($10, $25, $50, $100, $250, $500, $1000, for example).
However, suggested donation amounts work best when they correspond to a result. For example, what does a $50 donation allow you to accomplish? Consider adding a breakdown of how a given donation amount helps and what it allows you to do.
When possible, make the suggested amounts as specific as possible. For example, if you're an animal shelter, you could say '$87 allows us to rescue one dog per week'. You could have an $87 suggested amount, as well as a $174 suggestion (2 dogs), a $440 suggestion (5 dogs), etc.