100 € might be a bit too low. Mine is 800 € a week IIRC, but it also counts for payments via EC (Electronic Cash, i.e. paying with the normal bank account card). I once ran into it on a Sunday after just having paid for a week-long hotel stay. Luckily I had just enough money left to pay the train ticket back home.

Having said that, I also like the relatively low limit to contain the damage in case of skimming or card theft.