I oil my horses hooves once a week when it is really really dry out partly because he needs all the help he can get. You can certainly over oil them if you are not careful.. If you are getting a fresian you probably wouldn't need to worry. They have some pretty nice hard hooves.
And no horses don't need to be clipped. People clip their horses because they are riding them hard in the winter and when they sweat it is easier to cool them off when they are doing working. But if you clip them you need to have a blanket on your horse since they hardly have a coat to have through the winter anymore.
Whether or not you oil your horses hooves' depends on the conditions in which he is living. For example, a horse in a drought area in the West with little rainfall and no wet areas at all would probably benefit from the extra conditioner because the moisture would not be supplied to the hoof naturally. However, in an Eastern, heavy rainfall area, like where I am, I struggle to keep my horse's hooves dry enough. We have received a lot of rain recently, and his hooves are very soft for pretty much all of the fall through early spring so I never use conditioner on the hooves. This would just make the hooves softer and more prone to breaking off. Only when the hooves are overdried, brittle, etc. should conditioner be used IMO.
Depending on your weather conditions and your horse's workload determines the need for clipping arises. Just as general maintenance, I generally keep bridlepaths well-trimmed. During the summer, or for shows, I clip the extra fetlock hair and the whiskers around the muzzle and eyes. However, I leave the ear hair, esp. During the winter, for protection against biting bugs and for warmth. If I was going to show though, I try to clip at least around the ears to keep them tidy. Body clipping is unnecessary though in winter unless you can keep the horse very well blanketed (of course according to your climate) and the horse is in a lot of work. I wouldn't worry about body clipping though unless you are going to ride a lot. Hope this helps.