You can credit your miles to multiple programs, but you must credit ENOUGH to ONE of them to pass whatever its Star Gold threshold is. You have asked on the AC forum, so we have said 50,000 Altitude Qualifying Miles (earned on any eligible Star Alliance flights but credit to your AC number) including $3,000 (CAD) spend on Air Canada flights within the same calendar year (half the Canadian resident spend requirement). The Star Gold requirements are unique to each airline. Some last more than one year, some require more miles or different dollars to that airline. You need to comparison shop among the Star Alliance airlines you fly. After you have met the requirements for the airline that is easiest for you to get Star Gold, you can feel free to credit additional flights anywhere for the rest of that calendar year.
Your Star Gold benefits through AC would include security, baggage allowance, etc. on all Star Alliance, but the upgrades would only be useable on AC.
You really should read the airline websites rather than trying to get a clear picture just from forum member responses, because you can compare their requirements with your travel patterns without having to explain your travel patterns to us.