I'm not too worried about building up any piece of content before another - the code is designed to be pretty modular and responsive to change, I wouldn't write my way into a corner making it difficult to add something I know I'd like to add later. There's definitely a question of which features and systems the development priority will be on - I'm really just aiming at getting the main systems in place first - how the map works, how things grow, how characters in the game think, pathfind and communicate, that kind of thing. The beauty of this style of game is it can be approached in a lot of different ways (after the basics) so other than the order they're written in, spell crafting and alchemy don't directly affect other systems in the game (everything should indirectly affect everything else though - see drunken cats!).
That's great, and I'm glad you're going for a modular style. However, I'd still think about your end goal and build it towards that. Maybe not immediately, but after you've got the basic systems in you've got to make choices or it'll be just a bland colony game with different re-skins and stats for each race.
If you stick to dwarves - great! Make sure they're extra dwarvy and have something to distinguish them from DF, Gnomes and all the others.
If you go for Wizards - great! Make the gameplay based around learning powerful tactical and strategic spells, dueling other wizards, growing in power and building a huge library of rare tomes.
If you go for Dragons - great! Make it all about being a terrifying dragon, obsessed with hoarding gold and powerful artifacts.
Just don't make it dwarf fortress lite, plus dwarf fortress lite re-skin with a main character that can throw fireballs and make potions, plus dwarf fortress lite reskins with a dragon which is really powerful.