Your goal for the midgame is to acquire a Beacon. This is easier said than done however, because the recipe for it requires you to have progressed to Botania's endgame.

Before you can even start thinking about Botania's endgame however, you will need to get a Runic Altar first.
This requires Blood Runes from Blood Magic, a Witchery Attuned Stone and some basic Botania materials.

To start crafting runes, you will need Arcane Ingots from Aura Cascade, some more basic Botania items, some "easy" to find ChromatiCraft materials and a Tier 2 Blood Altar.
About those ChromatiCraft materials... you might have trouble finding some of them. Here is a hint:
"To bind the powers of fire and water to a livingrock slate, you first need materials attuned to these elements.
Finding them may prove a challenge however, unless you have a deep understanding of these elements.
Therefore it might be good to search out locations where these elements are concentrated, to learn more about them."

With these runes, you can start upgrading your mana production, and start working towards Terrasteel.
For Terrasteel you will need a Terrestrial Agglomeration Plate. For details, check the Lexica Botania.

With this Terrasteel, and an Aura Cascade Vortex Infusion setup, you can create Natura Pylons, which is one component of the Elven Gateway Portal.

The other component, the Elven Gateway Core, will require you to have been to the Witchery Dream World to acquire a Brew Of Hollow Tears.
Furthermore it will require you to get an Aura Cascade Arcane Prism. For info on how to get this, check the Encyclopedia Aura.

This will finally allow you to build the Elven Gateway Portal, which gives you access to Pixie Dust, which you need to craft a Beacon.