This really depends on a lot of factors...
1. Firstly, what is your combined budget for these pedals?
2. Can you give us examples of these effects in songs that you are trying to achieve? (e.g. you want envelope filter sounds like Flea from Red Hot Chili Peppers has in Sir Psycho Sexy, or the fuzz bass like Chris Wolstenholme from Muse has in Starlight.)
3. As already mentioned, you might want to seriously consider a multi-effect pedal if this is your first foray into the effects world. It's the most effect for your buck and lets you get your feet wet and see what you like and what you don't.
4. That all being said, if money were no object, and you were just looking for suggestions, and you didn't want to look into a multi-effect... my recommendations would be:
Envelope Filter: 3leaf Groove Regulator 2, or the Source Audio Bass Envelope Filter.
Overdrive: Xotic Bass BB Pre, Fuzzrocious Dark Driving, Dredge-Tone Bass Angler.
(I am unsure if you were looking specifically for an overdrive, a distortion, or a fuzz, so here are my recommendations for those as well)
Distortion: Fuzzrocious Rat Tail, Roger Mayer Voodoo Bass, bass modified BOSS DS-1.
Fuzz: Malekko Heavy Industry B:Assmaster (Silicon or Double Germ), Fuzzrocious Grey Stache, Smallsound/Bigsound Team Awesome Fuzz Machine.
Delay: Malekko Heavy Industry Echo 616, Electro-Harmonix Memory Boy/Memory Boy Deluxe, Empress Superdelay.
Chorus: Analogman Chorus (w/ depth switch or fixed deep option), Maxon or Ibanez CS-9, Fromel Seraph, Electro-Harmonix Small Clone/Neo Clone.
Synth: Octave/fuzz/envelope filter combination (e.g. BOSS OC-2 -> Malekko Heavy Industry B:Assmaster Silicon -> Source Audio Bass Envelope Filter), Electro-Harmonix Bass Micro Synth, Digitech Bass Synth Wah, Markbass Super Synth.