There's a table of Character Wealth by Level hidden in the Dungeon Master's Guide on page 135 (it's in Chapter 5: Campaigns for some stupid reason). Unless the DM says otherwise, you use this table to determine the starting gold of characters above 1st level. The given value for 10th-level characters is 49,000 gp. It's a general guideline, but not a rule unless the DM chooses to enforce it, that you can't spend more than half your wealth on a single item (though with the stuff you have that's not really relevant).