well the amtrak from dc to 30th st station is 2 hours. the subway goes straight to the stadiums (you take the market frankford line to 15th st, switch to Broad St line and ride south to the last stop). depending on if there’s an amtrak train scheduled that will arrive and leave philly at a reasonable time, you could do the whole trip in one day and it won’t empty your savings. it’ll be a long day though.

edit to add: once you reach philly you could even just uber to the stadiums, but traffic is ugly in the few blocks surrounding the complex