Well a birthday is a celebration of your life. (mind I never bother with mine

). Both wicca and Wicca are very different and wicca covers huge aspects of witchcraft that vary massively. But also misses many other aspects of witchcraft done by witches who are not wiccan. It is very hard to advise an eclectic because to be eclectic is to mix and match ways so only you know what suits you. Do you have one God or one Goddess, or both, or many? Again you may have no Gods at all and follow the land

You see how difficult it is?

Are you looking to incorporate an actual wiccan ritual into your birthday celebration or do witchcraft instead? Do you go the whole hog and use all the paranaphelia or ditch equipement and work without tools like so many others here do? So much of this affects what you can do and how to celebrate it.
Personally my thoughts are that an offering of cake and wine would do well. Mind my offering is usually apple juice or tea - far more of a sacrifice than revolting wine

I suspect then that you are new to wicca and/or magic so it is always best to fully understand what you are dealing with and go slowly. Therefore to give an offering such as cake and wine (or ale if you want to follow proper Wiccan tradition

) would be good as you are giving your thanks to the land or to the Gods for your life. Ask for guidance on your path and remember that it takes time to learn the ways of witchcraft and magic. Years in fact, your whole lifetime
And for the record I am a witch but I am not W/wiccan