If you aren't charging hst on your products and are making under $30k gross income there's no reason to register your business and have to pay the taxes.
Unless you are spending a lot of money on expenses then it might be worthwhile because you can offset the hst from your revenue with hst you paid but its really annoying doing this, trust me. A few things you can claim though are office supplies, materials, your business car repairs, food costs (restaurants, mcdonalds, etc. not groceries) There's a few more if I find my last years tax receipt I could put out the full list I was able to claim. It is good if you are forced to pay the hst but honestly it isn't worth it if you are making under $30k because you still have to pay your accountant to do the hst taxes and hope your expenses offset your income hst because most accountants will charge you upwards $500. If you're able to don't register your business unless you plan on spending a lot of money on expenses which would have to be paid no matter what.
Assume you spent $30k on expenses and grossed $28k income charging hst, you would be charged $3640 with your business being registered you would be rebated $3900 - $3640 meaning you would get $260 rebate after paying your hst, but with accounting fees and having to manage all your receipts it really isn't worth it in the end.
Never knew you lived in Ontario lol. Also don't take my $500 accounting fee as the industry norm you may find cheaper or higher prices.