It really doesn't matter, but some would say that making your own wand or such will add a more personal energy and connection to it. That doesnt necessarily mean that a store bought wand won't function in the same sense.
I would say that making your own tools is better than buying them because of the time and care that you put into the making. There will be more of your energy going into the tool, more thought and intention.
If you find objects for your Altar be sure to cleanse them well and to charge them with your intentions before using them.
Cleanse them under the light of the full moon, or a Selenite crystal will cleanse them.
I would say that making your own tools is more personal and adds a certain aura of your own to your items. I prefer making my own wands, knives, amulets, etc. because I can craft and metal smith, so if you hold any experience in crafting I would recommend it.
If time is a constraint for you or you do not feel you can craft, then buying what appeals to you most from a merchant is more ideal.
its not so much time for me its more of the metal smith tools plus as i have read from making tools you have got to leave them to cool natural this is the harder part for me as i have no shed and have got a cat and dot plus a child in the house thank you for your advice