Try it without and see how it goes. You need to figure out what works best for you, nobody can tell you what that is really. I also was told to use this and that and do this and that. My life was hell until I gave all that up and figured out what I REALLY needed.
The important thing is to be sure you take care of the skin around your stoma. Be sure you do not have any exposed skin. Be sure to be gentle removing the old appliance. As I believe was mentioned, push skin away rather than pull the appliance from the skin. If you want good wear time (and peace of mind) then your skin needs to be in great shape.
I normally do not use anything between my wafer and my skin. No adhesive remover, no skin prep, no spray, no powder. I remove the old, wash and dry (might even skip that if I am in a hurry), and slap on the new appliance.
Of course, if my skin looks a bit irritated then I usually dust a little zinc powder (or caldesene powder) on it and gently wipe off any excess so that you cannot really see it but you can feel it if you run your finger all over. Just enough to barely dust the skin really. If my skin is a bit itchy and irritated then I do the same but use Desenex powder instead. Anymore, I usually do not have to do either one.
If using a two-piece then I use a pea-sized blob of paste after I put on my wafer, just to fill in the minuscule gap around my stoma. Then I pop on my bag and I am good to go. If it has been a couple of days, I pop off the bag and reapply a dab of paste in the gap again.
If using a one-piece then I do use a very small amount of paste to ring around the very edge of my stoma before putting on the appliance. Once again, just enough to seal the small gap between the wafer material and my stoma. I usually will change my one-piece every other day (or third day if I am being lazy) just to be sure my skin is in good shape.
I also pay for supplies. I have tried various products and found a few different ones I like, that work well for me, and provide really good wear time. In other words, ones that provide really good value. So now I keep an eye out on eBay and even ostogroup.org to see if any of those are available. Sometimes you can even find an auction with various products and I suspect you could call and talk to ostogroup.org and probably get a variety to try out as well. Also, as mentioned already, you can usually get free samples directly from the manufacturer or even your local ostomy care clinic.
Hope this helps!
Dean