You don't have to buy used. You can buy online if you want to save money. Scubatoys, divesports are all reputable stores.
Also you don't have to buy the most expensive regulator. The ease of breathing of all major brand regulators for recreational depths are very similar. The annual warranty maintenance is just peace of mind. You can destroy your regulator within one weekend's careless post dive routine and can easily keep your regulator in top shape for couple of years.
For drysuit look at the classifieds section. I bought one for a ridiculous price which fits me perfectly and was really few dives old. Just remember DUI is not the only brand that makes drysuit
There are few other manufacturers who make perfectly good drysuit and have a very low used value on fleabay and the SB classifieds.