Ok, here is the way I set up my system early game. I built this above ground for the screen shots, but you can nest this below ground for aesthetics.
Bottom layer: 3x3 infinite water pool with the corners knocked out for hydroanges to be placed later.
Next, we make another pool offset by 1 block from the pool below. Fill it with water, the same as the first.
Next, make one more pool, and offset it again, so it is aligned with the first pool you created.
Next, place dirt in the corner of each pool, so the hydroanges can be planted later. You will need to replace some of the previously placed blocks.
Finally, add a layer of dirt above the top pool so you can plant your dayblooms and nightshades. You can place the mana spreader on either of the yellow clay blocks. These blocks represent the center blocks of each of the pools below.
So you can see even the furthest hydroangea can reach the mana spreader. I'm using a wand of the forest on the bottom left hydroangea, and it is showing it bound to the mana spreader above.
Finally, plant your day blooms and nightshades around in a checkerboard pattern. The flowers will not block the mana burst from the spreader, so don't worry about that. You can actually go much further with the dayblooms and nightshades if you wish as the range of the mana spreader is 6 blocks.
This little setup produced enough mana to get me started in botania. It took no time at all before I had created all the basic manasteel tools and armor. This provided all the mana I needed for my mining runs to keep the tools and armor fully repaired.
