Well, for starters I have to say that you probably aren't going to run anything too demanding at more than 1xIR with that computer. I don't know which settings you have already tried and what has worked so far (maybe you could clarify that a little bit?) but as I said the first thing I would do is to set the resolution to the lowest possible setting and go up from that.
Depending on the game there can also be different settings that give a free speedup, so I'd play around with those. Here is Dolphin's official compatibility list (including the game-specific settings), if you haven't tried it already: https://dolphin-emu.org/compat/
Depending on the game there can also be different settings that give a free speedup, so I'd play around with those. Here is Dolphin's official compatibility list (including the game-specific settings), if you haven't tried it already: https://dolphin-emu.org/compat/