simply wait 12 months for the metro to be finished and hop on a tram straight to the stadium more or less a door to door service :)
or if you don't want to wait 12 months i'd suggest the train from guide bridge the 216 wouldn't be too bad on the way there if you don't mind setting off very early to beat the traffic but the way back is an absolute ball ache they close the road to allow coaches through and traffic is at a stand still for up to 45 mins after the match plus getting on the bus is a challenge in its self with hundreds of people trying the same thing... admittedly the train is also cramped but at least you won't get stuck in traffic. walking it's about 4 miles so about an hour but theres certain areas i wouldn't fancy walking through at night on my own. taxi would be about a tenner but it'd be a ball ache finding one back. I usually drive and park about half a mile up the road out of the traffic tbf but i'm getting the train on wed for a few drinks