I suspect OP means "trial" since 90 days is mentioned.
I definitely recommend doing the trial to silver (cheapest option) rather than to gold. You'll get exit row access and slim chance of an upgrade. Fly 7500 miles and you retain silver. As soon as you've flown 15,000 miles within the 90 days - which you will once you've flown most of your trips you've mentioned - you'll be bumped to gold anyway. Keep flying within 90 days and you'll possibly make platinum or chairman's.