Impressions first
Rising impressions mean the site is being considered for more queries. That's the earliest signal a new architecture is working, usually two to four weeks in.
Position second
Average position across a whole site is nearly meaningless. Track position per page per query cluster instead, and only for queries that could produce a customer.
Clicks last
Clicks lag both. If impressions are up and clicks aren't, the problem is the title and description — not the rankings.
