Much will depend on what postal service you're able to use to ship your items and where most of them will be going (i.e. who you expect will mostly buy - US or Canadian buyers).
If, as you say, they are mostly small, inexpensive items (say, under $20?), as long as the weight is under 500gm, the length and width no more than 38cm x 27cm (the size of a #4 or #5 bubble mailer), and the thickness is under 2.0cm (3/4") -- and that is a critical restriction - you can ship by lettermail within Canada (cost varies by size and weight) and by Light Packet to the US. (for around $3 to around $10 according to weight). Obviously the lighter, the better. Small Packet gets you up to 1kg of weight and total of 90cm in dimensions (i.e. no 2.0cm restriction) for around $16. Small Packet and Light Packet are my go-to services for almost all my US shipments under $100.
The advantage to using Light/Small Packet is that you can generate and pay for the labels online through eBay/Paypal, and the parcels can be dropped in any post box or just handed over the post office counter. So you could do up the label in the evening and drop the item in the post box in the morning on your way to work. There is no insurance on either service though (there used to be, but not any longer). However, many sellers either self-insure, use 3rd party insurance, or just bypass insurance altogether for less expensive items.
There are insured and tracked parcel services available via online labelling, but the expense wouldn't be worth it for lower-priced items. I think most sellers agree those services, despite the discount, are for special situations.
Unfortunately only parcel services are available for online labelling through Paypal, but there is one venerable eBay seller who swears by the use of discount postage stamps -- bought on eBay for example -- so that's another possibility that might save you a trip to the P.O.