Let me just throw a spanner in the works over this "magic encourages suspension of disbelief, but mentalism encourages belief" divide. I strongly believe that magic should also encourage belief. If, for example, you decide that your character is a road-hardened card shark down on his luck who's having to prostitute his near-superhuman pasteboard skills as a performer since he was run out of Vegas on a rail, then everything you do in performances should be geared around inculcating your audience's belief in that character and the real skills such a person would possess. Ideally, you should genuinely possess most of those skills, but then also use the benefits of deception to appear to be even more impressive than would actually be possible. In my opinion that's a lot more powerful, and just plain interesting, than just being another magician.
Lay audiences don't really know what magicians are supposed to be, which offers us a great opportunity to elevate ourselves above any preconceptions they might have of creepy kids entertainers or gently diverting puzzle-setters. If your audience are made to understand what kind of real powers, training or insight make you able to achieve whatever miracles you're going to show them, you're suddenly doing real magic for them. Under this model, Ricky Jay does real magic, as audiences get to appreciate that he has genuine expertise in all sorts of arcane knowledge which helps him achieve his effects. No-one goes away from his show thinking that he might have just bought some gimmicks from the magic shop down the road as he's clearly steeped in a long tradition of magic and esoteric skills, and his demonstrations are allowing the audiences a glimpse of that tradition. To take another example, under this model, Slydini did real magic. Audiences understood that they were being misdirected, that this performer had perfect control of their attention. They saw that there was a real, near-superhuman ability on display, and therefore they were witnessing something genuine.
As regards this thread, my point is that I believe all of us should learn from the approach that mentalists take. We should decide on our "power", then acquire all the genuine skills and knowledge that would be expected to come with that power, only then using deception to give our performances an extra level of impossibility on top of that. Not, as in many performers' model of magic, use deception, sleights or store-bought gimmicks as a replacement for genuine skills and knowledge. So, learn to think like a mentalist even if you don't want to end up being one per se. Study acting, study psychology, study storytelling, study the greats of mentalism and consider what they do or did to make themselves believable.