1. What if gutters collect too much debris? I wanted to install some tanks to collect water from the roof as I don't have an "outdoor" area per se just a roof and a top floor veranda. But how could I maximize water collection? Via a massive funnel?
see if you can get a photo of your roof.
let me tell you what i did:
i have a steel sheet-metal type roof. i took a 3" schedule 20 PVC pipe (thats the thinner, drainage grade) and cut it lengthwise and opened up the crack until it "clipped" onto the edge. theres a small gap, so i get tree debris and sometimes pythons living in the gutter, but i dont care. at the end of the roof, i left enough space to glue on a 90 degree elbow and angle it down into a barrel.
on the other far side of the roof, i put another elbow down that goes into another barrel because my roof is absolutely NOT level, so some water goes one way and some goes the other direction. if you test out the level and find it pitches the way you DO NOT want, you could either turn an elbow up and put a small piece of pvc and a cap on the end so that that water is forced to go one way or you could add another 90 degree elbow and run another piece of pipe underneath that (attaching it to the roof beam with string or wire or something)
with a slight pitch so that the water runs toward the barrel of your choosing.
before the pipe goes into the tank, you can put screen material to catch the debris. i saw a guy in thailand that simply put a big, fine net over his rain pot so that the debris was kept out and the mosquitos couldnt lay eggs on the water surface.
2. My other idea was to have a series of tanks as a filtration system as I intend to drink the water myself (I don't trust bottled water (?)) or install a filter system with the tap. I can set up a distillation system to have drinking water. Lot's of things are in the thinking stages at the moment lol
if there is debris that collects on the roof, then the rainwater will naturally leach tannins from the leaves and debris. the water will be brownish, and that brown color will not drop out of suspension. running it through a berkey water filter will cleanse it, but the potable water will still have a tint to it. still, its completely drinkable.
as far as a distillation process, i found a guy who had access to a foundry where they could make custom stainless steel items. i gave him my schematic and he had it made for me: it is a stainless cone that collects distilled water vapor. you could do something similar to collect the water vapor droplets and have them collect into a glass jar.
3. The veranda is almost 3mx3.5m, it's tiled flooring with 2 drain holes however only one is operating the other is out of order. I've tried growing plans in pots and it started well until I had mealy bugs. Also loose soil was getting on the floor and with the scorching heat, it ended up becoming algae and I couldn't keep on top of it not being experienced enough. I also attempted to compost but that just resulted in a big stinky mess!
the mealy bugs can be sprayed with neem or you can crush them by hand-- thats a separate, resolvable issue. the pots need a tray underneath-- if you have a big hole on the pots (terracotta or whatever), do what i do: get some coconut fiber from the husk and block up the hole so excess water can seep through and the soil stays inside. if you dont have any fiber, look for something similar.
composting in the tropics should be easy with the heat. go to amazon or YT and look at some of the options and build one yourself. there was a guy who flipped one of those blue 55 gallon drums sideways and added a small side door to add the compost. he would roll it a few times per week to mix it and it worked well. you can mount a pipe on each side (like a roasting pig on a spit), set up a little stand, and turn it that way, too.