This will obviously depend on scheduling and the length of your stay, but assuming you had all options available to you, and you’re a neutral supporter, I would prioritize the games in this order:
1. Boca-River. The Superclasico of Argentine football, and a unique experience that is worth blowing your budget on. An event you’ll never forget even if you’re not a football fan, and if you are, it’s something akin to Nirvana. Better to see it at Boca’s home ground, the Bombonera, but harder to get tickets.