Not all use an alter. Altars can be made for many different reasons and in many different ways. There are many in the craft that make them for certain deities, traditions, and purposes such as healing.
I have a sacred space not an alter myself. True there is a table there but it is not just the table its the whole space I use to practice, meditate ect. If you feel like making yourself an alter by all means do so in what ever way makes you feel comfortable.
I use my coffee table as a altar. Its a normal glass and wood table. I keep al my tools in a box in a drawer. U don't have to create a special place. Before I cast a spell I cleanse the area and all tools with incense and that's it. Spell casting is not that difficult and u don't need fancy stuff. Depends on how u feel about it. If u want to buy fancy stuff go ahead. Its after all how u feel about it and how simple or fancy u want to do ur spells. Find what works for u.