Firstly, I'd get confirmation that this wholesaler will only deal with you if you are registered for VAT. I can't think of any disadvantage to them if you are not VAT registered. Perhaps they are looking for proof that you are in business.
If you are registered for VAT you must charge VAT on your sales. Consequently, you would then be able to reclaim VAT charged to you on your purchases. You must also make periodic returns of VAT charged and reclaimed to Revenue.