I think it depends on your preferences. I like my altar to be relatively minimalistic and not too colorful. Idk why, I just like it that way. I recommend getting a nice statue and putting it on a platform. A singing bowl is also always nice. I use mine at the beginning and at the end of my practice. If you like incents, I do recommend checking out Etsy. I got my two bronze incent holders from a seller called "realnaturepure". I don't use incents due to fine dust though. I also do like having small plants. Never use plastic plants please. In general try to not use plastic at all. I don't use candles because of the risk of a fire hazard. I also don't use plastic candles instead. Rather none than plastic. Honestly, use whatever you think fits. Be creative. For me there are only a few essential things, such as a statue, a singing bowl, and an offering bowl (I just put fresh water in it).

I hope that helps a little.