Bookmark a poll aggregator like RCP or 538, and watch the senate race averages like a hawk. Some will tighten in the coming weeks and some will break away with a clear favorite. Allocate donation dollars wisely to winnably close races where the Dem is not already a clear winner: 
The Senate is the key for us. If Biden/Harris win but we don’t lock in the senate, we’re going to end up with gridlock. For my dollars personally, I’m no longer giving to Dems that are up by 7+ because they don’t need it or Dems that are down by 7+ because it’s needed elsewhere
Iowa, for example, is a race that is not getting a ton of attention as some others but is both winnable and neck and neck close. So I’m moving resources into that race right now. I’d highly recommend you watch these averages and make those strategic decisions too.
The caveat is that these races are highly fluid. Who is up and who is down changes week to week but I suspect you will start to see some patterns as we get closer and can move resources around accordingly—not just your donations but your time for phone/text banking, etc.
Note also that RCP is not currently showing an average for Minnesota, Colorado or Georgia 2 because there are not enough polls but you can find the most recent polls on 538 or elsewhere I’m sure. They’ll probably have an average once we get more frequent polls in September
