Hi Sara, welcome. Presumably you're talking about walking the CF from SJPDP.
As
@Takahiwai says, spring weather is notoriously unpredictable and you could get the lot.
Whilst I agree that you can pick up pretty much everything you need in towns along the way:
you have to get to those towns first so ensure you pack enough layers to keep you comfortable down to zero degrees Celsius.
Layers are the key, for me that's a t-shirt, a long sleeve, and a lightweight puffer jacket. Good socks, long johns, pants, lightweight gloves (liner gloves) Buff and beanie complete the outfit.
Everything except the puffer jacket is
Merino.
Pants - I'm one of those people that use zip-off hiking pants year round.
Worst case Poncho or rain jacket over everything and I'm good to minus 5. Obviously there are all sorts of combinations to wear these in to keep me comfortable at a large range of temperatures.
Some people prefer polypropylene rather than Merino, and fleece jackets - your call. You've probably already got suitable clothing coming from Slovenia and living where you do.
The advantage of the Merino T-shirt is that it's good as a base layer but also on a hot sunny day (I still wear it at 30 degrees C) - plus I don't have to wash it daily if I get caught out, it takes at least two or three days before beginning to smell (unlike polyprop). But as I said, that's my personal choice.
Buen Camino !