1. Ditch the "cookbooks". Simply mix from Kodak or Ilford published formulae - which cover everything. Keep things simple.

2. Get a decent scale. Nothing fancy required. You don't need any other lab apparatus or equipment.

3. Generally unless you need an exotic compound, everything you get from reputable sources will be "technical grade" which is good enough for photography. Photographers Formulary is ok. I think Artcraft and Bostick are a little better for certain things. Not a big difference.

4. Be safe. Compounds best avoided: Pyrogallol, Catechol, PPD, strong acids/bases

5. General best mixing practices:

i) Use distilled water when mixing developers if possible. It simplifies things.
ii) Heat water to approx. 40C to mix.
iii) Proper formulas list the ingredients in the mixing order. Dissolve them one at a time, completely, in that order.