Sorry for the long post, but this isn't an easy-answer question. Here's my story:
I enclosed the area around my raised bed gardens and put down commercial weedcloth covered by pea gravel (at least 3" or around 7-8 cm depth) to keep out weeds. That was 1994. Since, soil has fallen in the gravel that I have to sweep up when I "weed" and weeds do pop up, but clearing them is much easier than traditional weeding. (Weed=Rake the gravel to one side, sweep up the soil, and pull or pour boiling water on the weeds.) I also have heavy clay soil, and occasionally, water pools on top of the pea gravel when we have days of heavy rain. See? The expensive answer isn't perfect either. What I have learned about all this is:
1. You need drainage somehow, even if it's a layer of sand under the gravel or digging a trench at intervals and laying some perforated plastic pipe to drain the water away, or you will have issues with your gravel base dissolving into the mud eventually.
2. You need a brick or timber boundary to keep this structure in place and make it hard for turf to invade the area.
3. You will have weeds trying to grow in just gravel anyway, so the key is to keep the gravel/sand base separate from the soil. You must have a good barrier, whether it is black plastic with drain holes punched into it under your pots or commercial landscape fabric that is supposed to provide drainage. Plastic is very cheap, but it tears and has to be replaced every year or so. My expensive landscaping fabric from 1994 is still going strong. I think it was worth the investment.
Bottom line: Overbuild your base and then enjoy the time/work savings later.

Good luck!

If you cover it with a wood mulch, as it breaks down it will start improving the soil. You may need to reapply every couple of years, but each time it will be working to improve the soil. Any kind of gravel will never do a thing to improve the soil, and grass, leaves, weeds, and other things will build up over time in a rock/pebble mulch, becoming very irritating to straighten out. With a wood mulch, someday that area might be a good place to plant things.

Thanks for the quick replies.
I should let you know that the mistake I have made up to now was using cheap fabric.This as deteriorated already after a couple of years.The area is brick enclosed and is a 1/2 circle.
Looking at the first suggestion I can see now were I went wrong.Cheap fabric and not enough depth with the stones I was using. And I think if where the water feature is going I can create a soakaway by using pea gravel under the water feature reservoir.