Last time we went via Northumberland Park (a strangely longish 22mins from Liverpool St) but only 2ph Sunday, so will be rammed. Does though mean the Redemption Brewery Taproom is doable before game, and wasn't too busy last year and the walk from there will bring you toward the away corner. For those making their way from Seven sisters the
Antwerp Arms looks worth a look and bus 243 would get you pretty close at 'Bruce Castle Park & Museum' stop.
Don't forget you don't necessarily need a travel ticket, just use any bank or c/card to tap in and out (train or tube, even if gate is open when exiting or you get charged the max) or just in on the bus, and use the same card to get best price total on the day.