I know I might be a bit late but, try making a cactus farm with a collection level every cactus level. I found my cactus farm on youtube and it has a 99% efficiency rate. Where as the typical cactus farm using string most commonly seen on factions has an efficiency rate of about 22%. Therefore you are losing almost 80% of your cactus, which adds up.
(skip to 10:09 for the cactus farm I use) Its just a 19x19 box with one high walls and water in every corner, side middle and very centre. It uses 64 sand and cactus to make one level, which is also good because therefore you get a stack of cactus every 50 minutes, per level. I currently have 16 levels so I get approx 1,024 cactus +/- the 1% loss due to getting destroyed every 50 minutes. Which is a little over 200k an hour. Not much but if you expand and build up it will be a constant influx of farming money without the need to replant anything or harvest, unlike many other farms.
Hope this helped lol