Greg's got the right idea: Start your clipless experiments with SPD, because they're ubiquitous and cheap to get.
But the fact that they're easy to acquire doesn't mean they work for everybody. When I fearfully entered the clipless world circa 2010, I started with a pair of Wellgo pedals that had SPD on one side, and platform on the other. Although I tried for a couple of months, I could never get SPDs to work for me; I couldn't get the cleat to snap into the mechanism reliably, and I didn't get any noticeable feedback when I was successful. So I alternated between repeated failures to snap in/thinking I'd successfully snapped in, only to find my foot flying free off the pedal/thinking I'd failed, only to find that my foot was unexpectedly attached to the pedal. This gave me much agita.
I then tried Crank Brothers pedals, and they were in my sweet spot. I've been riding CBs (Candys, the long-discontinued Quatros; if anybody's got Quatros to sell, hit me up) on my daily rider/pack mule (Raleigh International>Trek 720 touring) ever since. I find them easy to engage/disengage, and I feel a definitive SNAP when the cleat locks into the pedal, I also like having a little float, which CB provides. Plus, you can snap into Crank Brothers from either side, since the mechanism engages on all four of its faces. I have found that I can snap the spring holding the bits of the engagement mechanism in place, so I've got a couple of dead Quatros lying around. I haven't figured out how to disassemble the pedal so it's rebuildable; if I could do that, I could cannibalize the spring out of one pedal to rehab another.
My advice is to start with SPD, for Greg's reasons. If they don't work, there are a lot of other options, each of which looks/feels different. Figure out what it was that didn't work for you on the SPDs, and let that guide you to one of the other candidates (CB, Time, Speedplay etc.). If none of your available clipless options work for you, platforms are fine - with or without toeclips/straps.
Practice on a lawn; you'll fall down a lot at first. Most clipless newbies are nervous about disengaging at speed, but that almost never happens. You're most likely to fall over when you're going slow, or when you're stopping, especially of you have to stop suddenly and your instinct to disengage doesn't kick in fast enough to get a foot down. The half-dozen or so times I've fallen while cleated in have all been at red lights that had just turned as I approached. Since I was going slow when I fell, I mostly felt embarrassed, clumsy and stupid, rather than panicked. Passersby asked if I was OK, but I wasn't; I'd just bike-doofused in front of witnesses 😬
Peter "pride goeth right when you fall down" Adler
Berkeley, CA/USA