We used Seat Geek last month and were able to find reasonably priced tickets pretty easily. However, just know that the grandstand seats are oooooold, so our tickets were past first base, but they faced directly forward, staring at the Green Monster. You had to angle yourself the entire game to see what was happening at home plate.
That said, we had a great time. There's lots of history to see, so if you're into that sort of thing, allow time to walk around the park. There's display booths at the front that goes through the years and even if you don't have tickets, you can still get pretty close to the Green Monster. They won't let you ON it though.
If you Uber and are pretty close but at a dead stop in traffic, it is 100% faster to get out of the car and walk the few final blocks than trying to be dropped off in front of Fenway.