The order I'd get things in:
Cabinet/materials
Light setup
Extraction/environmental control
Pots
Medium
Seeds
Nutrients
Smell prevention (generally get this kind of thing last 'cause they don't generally start to smell for a while)
you want to make a decision on the layout 1st, decide if you want to split the cabinet up for a mother/clone area etc. Work out how much space you have, then start worrying about how much light you need for that area, then you want extraction etc to control temps, and do a dry run for a day or so to work out any kinks. Then you can start worrying about seeds and how your going to grow, soil, hydro etc.
They don't need nutrients for the 1st few weeks, or longer if you get slightly fertilised soil, so nutrients are not a top priority if you have to buy things in any particular order, in my opinion.
Stay Frosty and good Luck!