I totally second take a trainer with you when shopping, so easy to find something that you really want to make work, you need someone who will point out all the reasons why you shouldn't buy it. It would of saved me a bunch of stress, money, and ultimately a bad accident if I had gone shopping with a trainer from the start.
Golden Rules from Golden Horse
1) Buy the horse that you need NOW, never make the mistake of thinking "This will be the ideal horse for me when I am fitter, thinner, a better rider, more experienced" No, there is a horse for you NOW, buy that one, and if needed in the future look for the next step.
2) No youngsters, in this partnership one of you should have experience, if you are lacking it, make sure your horse has it.
3) If possible have it clear in your mind what it is you want to do with your new partner, if you want to go cutting cows, a 17.2 hh warmblood, would not be your choice, but if you want to do dressage a zippy 14hh QH would not be your first choice.
4) Write a list of what you think you want, and talk it over with your trainer so you both understand what you are looking for.
5) Neither color or breed really matter, do not get set on one breed, neither discount one, just look for the type of horse you want, most breeds have all sorts of types, and discounting ..OHH Arabs, for instance, because they are crazy, could mean you miss a gem like my old Arab, who is definitely novice friendly.
6) While not a rule, it is good to keep in mind, Good horses aren't cheap, Cheap horses aren't good. No it isn't 100% accurate, there are exceptions to every rule, but for a first horse a good budget is helpful.
“Never attribute to malice that which can be attributed to stupidity”