Don't spend it. Save it for armor, with runes/insignia maybe and signets of capture and other skills you might want to buy. And don't worry about leveling. Just play through the campaign, explore and do quests, etc. Use the best gear you find from looting your victims, upgrading as you kill things and find better stuff.
For the record, you can get max damage, req 9 swords/axes/hammers/bows/foci/wands/staffs/shields from collectors. With all three campaigns out there, you can find them with most any inherent mod from a collector somewhere. With only Prophecies you can't get to all those collectors yourself, but people will sell you collector gear for 1-2k or less
(some will just give it away.) Feast your eyes on the
GuildWiki Collector List.
Collector gear won't come with prefix and suffix mods, but you can gather functional mods as you kill too. Keep an eye out for mods you like on your drops and use an expert salvage kit to get them off loot if you want to put them on a better weapon.
Max weapons? That kill stuff just as fast as the uber-leet-zomg-100k+500ecto weapons you see in high end? Yep! The catch? - they're blue texted, not gold texted and they don't look the same on the screen.

In GW, elite gear is about rare skins and oddities, but even poor players can have max gear.
You really don't need much gold at all to play this game. Once you've got your character maxed out, been around, have your max armor, etc. you'll start to accumulate gold as/if you keep playing. Worry about buying snazzy-skinned stuff then.
Cheers!