Hi – advertising to SMEs is hard; there are a lot of them and many channels. I’d suggest linking in with industry and support groups for the SME sectors you want to serve – which may mean you need to narrow down to some subsectors. Eg partner up with the hospitality association or retailers association. Think about advertising in trade journals or online on sites they are likely to frequent. A mix of paid and editorial might get you there in some publications.
The main advice is to be specific – you’re a start-up. You can’t sell to the 60,000+ businesses in NZ. Where will your offer have the most relevance? Which sectors have a defined grouping? Start there.