Although most clubs will let you sail anything suited to their water, it's more fun to sail a class which has a good following at that club, so you will have a ready source of hints, tips, spares and chat. Two handers are more sociable and allow you to share all expenses and effort, single-handers mean you go sailing when you want. It's up to you. If you're considering a two-hander, you need to ensure that your proposed partner wants to sail approximately the same amount that you do, whether that is four times a week or once a month. It is always possible to find another partner, but you might as well start off on the right foot.
Some dinghies are easier than others.
A performance skiff may not be the best boat for two novices. There is a thriving second-hand market in all the established classes, so you can always trade up. Wooden boats need loving care. Fibreglass boats need some attention, but much less. There is no point buying an expensive dinghy which will only get sailed twice a year.