My 6 year old has his first French birthday party tomorrow. In Ireland I usually give/receive gifts that cost €10-15, is it the same here? I also usually give a gift receipt, do people do that in France? Also, are you expected to stay or drop your child off and leave?
No party bags, professional entertainment, its normally just take a present.
In my experience presents from the invited children are fairly common, and it is generally considered polite to bring small presents (your price range sounds about right), although not obligatory. Peer pressure tends to play an important role here.
As to parents staying or just dropping off, I would say mostly “dropping off/picking up”, especially if you have no direct links to the parents. You could always invite them to stay, but don’t be surprised if they disappear as soon as the kid is at the door (or gate) and after having asked what time to pick their child up. I have found that it varies on the ages of the children involved - when my kids were little, the parents almost always came in at least to drop off their kids, but as they grew older, just generally tended to be dropped off and picked up at the gate (unless I personally knew the parents). I tended to do the same with my own kids when they were invited to birthday parties.