Reddit reviews The Cake Bible

For vegan cake and frosting recipes, Isa Chandra Moskowitz and Terry Hope Romero's Vegan Cupcakes Take Over the World is outstanding. For decorating (and understanding cakes), Rose Levy Beranbaum's The Cake Bible. Your library might have copies.

For decorations, I would first just start googling "cake decoration", and look for videos that show technique. If you have no decorating experience, start practicing now. Cake decoration does require some basic equipment, like piping tips, offset spatula, etc, depending on how you want to decorate it. Creating complex designs will require more specialized equipment to work with fondant, pastillage, etc., and those things take lots of practice. You can purchase some pastillage decorations like sugar flowers (food-safe but inedible) from local baking supply shops or online.

You can practice piping by making "practice frosting" (basically Oreo filling):

• 10 oz veg shortening
  
• 16 oz. powdered sugar
  
• 0.5 oz. water
  
• 0.75 oz. light corn syrup
  
  Put shortening in the bowl of the mixer, then alternate beating in wet and dry ingredients on low, then increase to medium and beat until smooth. Use it to work on techniques on wax paper-covered plates. You can re-use it; just scrape it into a Ziploc when you're done and stick it in a cool cabinet, and it will keep for ages. Re-beat it if you need to smooth it out. If it's too loose, stick it in the fridge; if it's too stiff, warm it gently with a heating pad. You can make piping bags out of waxed paper or freezer bags, and a basic tip set is inexpensive.
  
  If you're really going for a vegan-themed cake (wasn't sure if that's what you were requesting), I would definitely make marzipan fruits and vegetables. Marzipan is delicious to eat and it can be forgiving to work with.