Q. What goes on my altar?
A. Though there are some specifics to altar tools and placement if you are following a very traditional type of Wicca (like Gardnerian), generally people choose what they want for their altars based on their beliefs and interests. Items to represent the elements are very common, such as a candle or chalice for fire and water. A selection of crystals, statues and natural items can all be included too. It's very personal. I have a longer article on altars you can see for more info.
On a side note, you don't necessarily have to have a permanent altar to cast spells or practice witchcraft. You can set up your tools and supplies on a clean table or counter top whenever the need arises and just take it down again later.