Try starting with armor and weapon crystals. Most have no limit to use, the only non-oermanent part of themis the ability to swap them out for new ones. If she's good, a lesser fiendslayer crystal is often a useful buy at 3K, making the weapon good aligned and doing +1d6 damage versus evil outsiders. Te ultimate prize for her would likely be a greater truedeath crystal, price of 10K. Lets you SA undead, as well as some other things. For armor and shield crystals, the Ironward series, clasps of energy protection, and arrow deflection are all generally useful. Crystal of glancing blows is nice to avoid grapples, and crystal of alacrity is +5 ft speed and stacks with boots of striding and springing.
For weapon enhancements, Shadowstrike is 1/day, lets you get +5 ft reach and make the target flatfooted. Cost: +5000 gp. Hideaway, +2000 gp, lets you shrink the weapon by two size categories and back as you please. Neither has a market price mod, so it becomes a better deal the more you level up (as it doesn't drive up the cost of adding more to her weapon). If she really likes using sneak attack, she canpay a +1 bonus for +1d6 SA with Deadly Precision, though I don't think that's worth it until the weapon is +5 already.
For armor enhancing, I like blueshine if she uses metal armor. +2 hide, and armor is immune to acid and rust, all for just +1500 gp. For a +1 market price you can get Mobility, which gives the feat of the same name, making it much less painful to pursue feats that require it, like Spring Attack.
As a Rogue/Bard, I assume she has UMD. Eternal Wands let you get arcane wands that are 2 uses/day instead of 50 charges, this may be useful to her.
Dragon Mask, 4000 gp, gives a swift action 2/day see invisibility for 5 min. each, useful to any character.
Boots of Agile leaping are one of my favorite items in the book. They only cost 600 gp, or 900 to tack onto an existing set of footwear. They let you make jump checks with dex instead of str, and most importantly, let anyone with 5 ranks in balance stand from prone as a swift action w/o provoking an AoO. Most useful for tripping builds, when things go wrong, but a nice defense for anyone with the ranks.
Any of the boots that let you teleport are great. Best is probably Boots of Sidestepping, which let you take a "free" 5 ft step as a swift action 3/day. In other words, you can take a full attack (maybe with SA?) and then move away 10 ft to deny the foe doing it to you.
Gloves of Fortunate Striking fit the luck theme. 1/day you can reroll an attack.
Mantle of Second Chances is expensive at 12,000 gp, but lets you reroll ANY one roll 1/day, also fitting the luck theme.
Charm of Counter Song is dirt cheap -- 500 gp -- and lets you 1/day use it as an immediate action, presumably to interrupt a sonic attack from the description.
Chronocharms are also 500 gp and 1/day. Horizon Walker and Grand Master are the versions most useful to anyone, letting you take a move as a swift action and gaining +4 AC vs. one attack, respectively. Laughing Rogue may also be useful.
Amber Amulets of Vermin to summon a loyal giant insect 1/day are fun and inexpensive.
Shiftweave is cheap and great to quickly change outfits if doing some underhanded work.
Belt of Ultimate Athleticism lets you take 10 on lots of athletic and acrobatic skills without limit, it may be worth it for Tumble alone. 1/day you can take 20.
For item sets, check out Fleet Warrior's Array and Regalia of the Hero (especially badge of valor)
