It depends. Conjuring oil, anointing oil, blessing oil, cleansing oils, etc... Depending on your path, can be a special mix. For example Von Von or some say Van Van oil. It's easier sometimes to buy these rather then buy all the stuff to make your own. However....if its something silly like "make a wish oil" just put a drop in your bath and make a wish....the only magick there is making your money disappear.
As for Talsmins, yes they work. But like what's already been said, you have to put the work into it. However, I'd something calls to you ( just feels right ) then it's worth the purchase. You still need to put the work into though to make it your own.