Seahorses, to tell you the truth, are not that hard if you have had prior experience. Read up on the subject before you get them..if you don't...I guaranteee you'll have problems. I researched about 1-2 years before I bought my first seahorse, and IMHO..it helped out so much. Whenever anything would go wrong, or the like, i'd know what to do. No hurrying and trying to get to the lfs or computer to check out what I need or what's going on.
Like said, please have SOME experience with general saltwater upkeep. While I said seahorses aren't that "difficult" like everyone says, they will not tolerate beginner's mistakes. A beginner to saltwater not only has to worry about learning all the nooks and crannies of the saltwater hobby, but piling seahorse care on top will probably end in disaster. Seahorses, unlike other fish, have susceptibilities to diseases you may have never heard about, they can get out of control in only a few days..diet is much different, 3 feedings are a must per day, and many more. When you research them...it's like learning about a whole other kind of tank and maintenance all over again.
Demon, there ARE many people who have had seahorses for their first saltwater fish, or even first fish to begin with. Was this usually the smartest thing to do? Probably not. Out of the few success stories out there, do you know how many more unsuccessful stories there are? There are literally thousands but you won't be seeing those anytime soon..people are more likely to post successful tries rather than a failed attempt... Sorry to say, but these aren't just something you do on the spot. While research helps out and it's one of the most important things to care for them, experience is even higher on the charts. While you may KNOW how to care for them..it means almost nothing if your just doing it for the first time. Starting out with regular saltwater fish gives you the trial and error process needed for seahorses...sorry if I sound rude about this.
Seahorse.org...is THE best place to start out. There are other forums dedicated to seahorses on the net..but are essentially worthless compared to the vast knowledge, caring, and dedication of the members there. Not only will they help you out with any problem but along the way..even make you feel welcome and along with it...there are already over 20 articles on the care, breeding, and identifying of the different species. Even a general tankmate chart.
As for the best beginner SH, stay away from dwarves, not the easiest like most say. Trying to kep the larger species of horses are much easier than getting into the nano realm of the dwarves. Also, if your just starting saltwater. Getting into it with a 2 gallon nano with seahorses which require feding of newborn baby brine shrimp three times a day is going to be very difficult. Erectus, reidi, kuda, etc. are all beginner friendly species. I started with a reidi, and have had only two problems since buying it..it having babies out of the blueonce...and having to do a pouch evacuation on it after my temps dropped by more than ten degrees.
Hopefully I didn't scare you off from seahorses, but please take my words to heart. Get some experience, learn along the way, do research on them, then you should be ready to get some. If you got some right away, there is a possiblity things could go wrong, and it would be shame to see that happen to someone new to them. Most after having that experience, never keep them again or advise others to stay away from them. I hope my info helps you with keeping them in the future, and if you have anymore questions feel free to ask! Good luck