I'm assuming you're going to be an obby mauler. If so, get 5 attack. It increases your combat by 1, but also increases the chance you will hit high by a considerable amount. Definetly worth it.
After that, I'd work on the strength some more. There's not really a lot you can do in F2P, especially as an obby mauler
If you're planning on staying F2P; I'd get 40 Attack so you can atleast weild Rune weapons.
If you're planning on upgrading to P2P; I'd get 60 Attack so you can weild Dragon weapons and then do both; Lost City and Monkey Madness.
After you've done one of the following, just keep leveling your Strength. But.. you can also level your Range and Magic if you're going to become P2P as they're a good combination with a DDS.