What do you mean "bonfire at level 8"
When you find Undead Bone Shards and burn them at the Firelink Bonfire it upgrades your bonfires. Each time you upgrade it makes your Estus Flasks heal a little more when you use them.
So there's Estus Shards you give to the blacksmith to carry more flasks and Undead Bone Shards you burn at the Firelink bonfire to upgrade how much an Estus Flask heals.
As you upgrade when you rest at bonfires it will say the bonfire level as well as say "Estus +7" etc. next to your flasks in the item bar.
Also if you find Ashes give them to the merchant lady in the hall on the way to the Blacksmith and it will unlock new things for her to sell.
Also you'll eventually have so many Titanite Shards it won't matter. Plus you can buy them and Large Titanite Shards later.
It's the Chunks, Scales and Twinkling that are harder to come by.