Hi. We have tried various things. The green mesh which is cheap from garden centres lasts only one season. A bit more expensive initially but should last for quite a number of years is knitted black netting available in various widths and lengths from LBS horticulture (google them). For the hoops, we use blue alkathene water pipe - as used by the famous Geoff Hamilton. Stick a piece of cane in each end to go under the ground, and space them every 4-5 feet. For brassicas which are taller, I have been using canes with tennis balls on the top, but found they froze solid in the cold. I like the idea of coke cans if you are a coke drinker, and we have also used individual plastic water bottles when we can get them - beer bottles are very jolly but unfortunately too heavy
. I have found that flower pots are not secure enough and blow off even when held down by the net. For the edges of the net, I have threaded canes along the netting, then used pins made of old fencing wire (the thick stuff we use instead of barbed) to hold the canes down. Whatever you use, it looks good when it goes up, but weeds and weather all have their effect over the months.
Please also make sure to check your cage every single day as birds get in, no matter how bird-proof you think you have made it, but they can't get out.