Right... Let's get this answered :o!
Here's a set I would personally want to use:
Exeggcute @ Eviolite
EVs: 36 HP / 196 SpA / 76 SpD / 196 Spe
- Solar Beam
- Hidden Power [Fire]
- Sleep Powder
This set is to be used alongside a Drought user (Vulpix basically). The thing is, Exeggcute is heavily outclassed by a number of LC Pokemon. Most prominently, it's bulky sets are outclassed by Foongus and Ferroseed (to an extent), and offensive sets by Bellsprout. It used to have the niche of tackling Meditite, which was a huge threat, but now that it's banned it is no longer a much appreciated 'mon.
The one thing this set has over Bellsprout though, is that it's not as sun reliant and it's teammate Vulpix can run items other than Heat Rock, like Choice items.
Modest Nature for max damage, as Chlorophyll remedies speed issues. As this is to be paired with a Vulpix, Solar Beam is opted and HP Fire is thrown in for coverage. Psychic for STAB and Sleep Powder for status.
Hope I helped!