It depends very much.
There are a total of 8 different blessings one can have.
7 for PvE and 1 for PvP.
For the PvE you have these options.
You can run on the temples and get the blessings for their 'normal price'.
You can buy the charms from other players, obtain on quests or drops which may be cheaper depending on the server and your level.
You can buy them with TibiaCoins on the Store. Which always have the same price, most of the times it's very expensive (depends on TibiaCoin price)
You can buy them from Henricus IF you've finished the Inquisition quest.
NOTE: Henricus sells 5 out of 7 blessings for 10%+ of the normal price. You Must have finished the Inquisition quest.
Every bless reduces the chance of gear pieces being dropped upon death as well as the backpack.
At 5 blessings the chances of dropping your backpack and gear pieces get to 0% meaning you can die and no item will be lost on the process.
Blessings 6 and 7, are considered ' extra blessings ' they are more expensive than the first initial five and an only be bought by premium players, one is in northern banuta accessed by the ground level on a -1 cave, the second on north-western svargrond on a +1 mountain.
The extra blessings reduce even further the EXP and Skill loss.
For detailed information on Blessings, the formulas used, location, price formula and everything else please check here.