When I was around 10, I started coating a q-tip with soap that I learned to let dissolve a bit in warm water. Then I would roll the cotton tip all around in the soap which acted as both lubricant and irritant. By the time I was 11/12 and took baths alone and had my own bathroom on a floor where no one else in the family slept except me, I would insert these soap infused q-tips virtually every chance I had to take a leisurely bath.
They caused a burning sensation, but I found it pleasant and gratifying, especially when I knew I would be alone upstairs for the evening.
So q-tips were the first things. Admittedly small potatoes, but you gotta start somewhere. I tried other things later like pens or handles of toothbrushes but I never cared much for these, except for candles, which were almost as fun preparing by shaving and trimming and shaping, as actually using them ... the sense of anticipation and trying to think up odd shaped tips was an arousing sort of sensation, sometimes making me shiver and shake by imagining using them ...
These were my self insertions. But prior to that I would on occasion be given suppositories by an aunt or grandmother, mainly as a matter of normal protocol prior to being given a bath, without really needing them.