I'm a certified trimmer (DAEP) and I can tell you that while trimming is not brain surgery or anything, there is quite a bit to it and you can easily mess things up if you're not careful. Interpreting from a book or DVD can be very tricky. There was so much I just couldn't "get" until someone showed me hands on.
My suggestion would be this - find a good farrier or trimmer that you trust, develop a good working relationship with them, and then offer to pay them for their time in helping you learn to maintain your horse by yourself. They can suggest a brand of rasp and hoof knife. You won't need nippers because you'll be maintaining the feet frequently. An apron is definitely a plus as the knife can be dangerous if it slips, but you can find inexpensive ones. You can get by without a hoof stand and maybe purchase one later down the road.
If your horse has good, sound, solid healthy feet that tend to wear nicely, you will be fine to learn to maintain them yourself. If your horse has any kind of pathology like cracks, laminitis, underslung heels, etc. then you might find it's too difficult to keep the horse sound by yourself.
You can have the farrier or trimmer come out say 2x a year to check on things and make sure you're doing ok.
That's exactly how I started, and in time I ended up doing a year long certification course, doing an apprenticeship, and now I have more clients than I can say grace over. LOL. If you don't want to trim for other people, then a certification is not needed.