Environmental controller help plz

i'm wanting start project control environment in workshop/greenhouse.

variables control in order of importance

lights on timer
temperature via fan speed  control temperature
temperature #2 if needed control heater in winter if possible
humidity-relay turn off/on dehumidifier
timer turning on water pumps every 2-3 days set period of time.

after researching these needs, seems arduino can these things, i'm not sure version buy , start out with.  assume should start 1-2 of these first instead of trying whole project i'm sure there issues stumble through , troubleshooting should easier less variables.

also, if have approximate cost figures how things break down too.  not sure how cost effective in end.  trying save myself time , clean wiring etc..., if can't afford it, it's moot point.

thx

pick 1 item.

say temperature.  select desired temperature sensor, 1 , program make sure can work.

once have reading, attempt turn on heater when cold, or turn on fan when hot.

once have done, pick next thing.  if choose temperature , humidity sensor, make work.

everything asking documented on web examples.

google garden arduino 

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