This is just information I have gathered from my time playing with this mod and it's counterpart to make them fully look like dragons instead of the weird human/dragon hybrid things.

BASICS:
Start the game as you would any other playthrough and explore as normal. While hopping around to different planets, primarily the early ones, you might come across small groups of Draconis in tents, caves, or buildings on the surface. They are generally merchants that sell some of the basic items from the mod and occasionally some rarer items from it. Check them out when you can as they can have some pretty good stuff.

TECHS:
Progressing a bit further after reaching the outpost you will get access to the different vanilla tech quests. After going through the early ones of them you will get another one specifically for the Draconis techs. Upon completing it you get access to your flight ability and dragon breath ability. Flight is slow but allows you to boost while holding 'UP' + 'JUMP(SPACE)'. It drains your energy quickly but allows very fast flight. Your flight direction will be towards your cursor so be mindful of it as you fly. There is no fall damage so feel free to try it out however you will. The dragon breath is just a directed short fire stream that also follows your cursor and drains your energy quickly. It visually looks off due to it using roughly the flamethrower's effects so I generally don't use it. However it is fairly strong.

SPECIAL FEATURES:
The other two additions you can find are a gas pump and the special dimension door. They each spawn with similar looking ground and background styles around them and only spawn above ground from what I have seen. The gas pump is just a shop you can use to buy fuel for you ship. There are several options in it and it offers an alternative to mining moons. The dimension door is a one-way gateway to the Draconis homeworld/outpost like area. You get access to some very basic shops, some more gas pumps, a special shop with a few cosmetics and the Flux Cores for item upgrades, and the tables to make spell books.

SPELL BOOKS:
You can't buy or find the spell books normally. When exploring worlds and finding Draconis merchants, there is a chance they will sell an elemental scroll. Usually sold for around the 10,000 pixel mark, they grant you the knowledge to craft a spell book yourself of the scroll's type. They usually use some amount of late to end game materials and leather. They are 2-handed with a main and sub attack that both cost energy to use. WARNING: If you find the fire type (Dragon) scroll and spell book, beware that it's secondary attack will immediately destroy surrounding blocks in a fairly large area. It can be used for tunneling or clearing out large areas quickly and erratically, but is quite dangerous.

CRAFTING:
Some of your basic gears can be made at the anvil like normal, but advanced gears are made at the Hellforge and Synthesis Lab. These are accessed by upgrading your Inventor's Table after which they become unlocked to craft. The Hellforge gives access to the weapons and armors. Most of the weapons can be crafted with just normal materials and the Flux Cores that are bought on the Draconis homeworld/outpost world. The other items and the armors require the Synthesis Lab to be made as well. The Synthesis Lab uses basic components like water, coal, and wood logs to craft into basic components which are then combined in various numbers to create different elements which are further combined in various amount to create some of the actual materials you need. It is a very lengthy process to refine everything but is easy to do after getting just a handful of basic components to start with. It also don't help that you might need thousands or more different Lab materials to get enough to make some of the basics and the crafting speed is slow. Upgrading most of the weapons and armors is done by getting some materials as well as the previous tier of whatever you are upgrading while not all weapons require Synthesis Lab items.

EXPLOITS (READ AT OWN RISK):
Both the Gas Pump and Draconis Gateway can be harvested and picked up to place wherever you want.... even in your own ship. This also works for the Spell Book crafting station if you manage to find a Draconis building spawn on a planet that contains them.

The Synthesis Lab turns simple water into infinite money. Creating 1,000 hydrogen using 10 water creates a stack of hydrogen valued at 60,000 pixels. This can be done infinitely and can be sold to any merchant around.

The Draconis flight tech can be used to travel very fast for a long time. A technique you can use to get the most out of your flight boost is to hold 'UP' and just tap 'JUMP(SPACE)' to continually boost. Letting go of your boost button simply reverts you back to the slow flight speed instantly while doing this tap method allows you to basically fall sideways quickly to gain a lot more ground. Super effective if you want to fly around a given planet to search it for more settlements or one of the two other additions with this mod. This also works going up or down as well to gain more speed.