Here's a build, but there are holes left in it. Basically anything not being used for a deliberate purpose, I left blank, assuming you'll fill in what makes sense. There are also a lot of things marked as suggestions, usually because something isn't necessary, but would be useful.
Starting
Race: Human
Stats:
Str: 16
Dex: 13
Con: 12
Int: 14+2 (human!)
Wis: 10
Cha: 14
Feats: One for first level, one for being human, and one for third level, plus combat casting from being an arcane duelist.
Martial Weapons Prof(Greatsword)
Combat Expertise (2nd feat curiosity of being human)
Suggested:
Improved ([Combat Maneuver])
Weapon Focus(Greatsword)
Combat Casting
Equipment: At lvl 3, you should have 3k gold.
Greatsword (50gp)
Light armor- Chain shirt if you don't care about the armor check penalty, leather if you do.
Suggested:
Make that greatsword masterwork and enchanted, which will make it 2350gp. Best choices are Keen or Spell-storing, depending on whether you want to be more of a damage dealer or a mage/trickster.
Spend the remaining (You should have ~550gp left) on outfits, food, a couple of throwing daggers, whatever suits your fancy. Soap is always nice to have.
Skills
You need a few skills maxed, as they're high priority. But you should have plenty of other skill points to throw into whatever you want.
Skills to keep maxed: Perform, Concentration, Intimidate.
Skills you want depending on focus: Stealth, Perception, Slight of Hand, Spellcraft, Diplomacy, Disguise. Knowledge of all kind might come in handy.
As you level up
Stats: At fourth level, fix that dex to a 14 so as to get the bonus modifier. Then, sometime in the next three stat-ups (occurring at 8th, 12th, and 16th level) you need to spend two points in charisma so you'll be able to cast your 5th and 6th level spells on time. I would recommend putting the two unmentioned stat-ups on the same stat, since that's where modifiers come from. I'd also suggest dex, since you're AC is going to be on the low side. Strength or Charisma would be decent, depending on whether you cast spells or swing that greatsword more often. (Here's a question of mine on the comparison. How important is charisma for a 3.X bard?)
Wisdom, intelligence, and constitution are all sub-par choices- since you'll get the modifier at level 20, it's not like you're going to be getting a lot of skill or hit points from this, and wisdom isn't really the focus of anything you're doing. They don't hurt, and if you want them go for them, but you'll use the above far more.
Feats: Alright, there are a lot of choices here. The sneaky rogue part of you doesn't need many feats as long as your skills are up to par, so most of your feats should be going to the fighter/caster part of you. If you want more of the caster, metamagic is always fun, but you might not have the spell levels to do much with it. I suggest putting most of yours into doing fightery things. The weapon focus/specialization chain is very useful, Improved ([combat maneuver]) usually chains into something fun if you don't mind the added complexity. (I'd suggest improved trip.) Combat Patrol could be fun if you need to protect others.
Really, this is going to depend on what you want to do. The more middle of the road you are, the lower everything else is going to be. Feats seem to help the fightery bits of you more from what I can see.
Equipment: Keep your armor in good condition. If you get a large load of gold, look at getting a +2 greatsword. This will depend on how much gold you run into in your travels. As long as your armor and weapon are solid and kept up to date, and have fun.
Skills: Keep what you had maxed maxed. Look at getting skill synergies when you can, but most skills are situationally useful, and some of them may come up more than often. Pick skill checks you seem to be failing, and improve those. I'd suggest a second perform skill for flexibility.
Honestly, with a jack of all trades like this, there are a lot of different ways to build him. We can't optimize for one ability or situation, because you're trying to be good at most. But, as long as you can keep your weapon damage solid and your spellcasting at par and a crudload of skills, you should be able to improvise any other situation.
Best Answer
Your build includes any and every mechanical option that is relevant to its functioning the way you intend it to. In short, “build” means what you say it means.
If you say that your build doesn’t care what weapon you use, then the choice of weapon is not part of the build.
If you say your build requires a melee weapon of some sort, that is part of your build, but which particular melee weapon is not.
If you say your build needs a melee weapon with reach, then that is part of your build, but any number of polearms can fit the bill.
If you say your build needs a holy avenger specifically, then that is part of your build, and finding one becomes a requirement for someone interested in playing that build. Someone suggesting something so specific should probably include discussion on how to accomplish that (most likely through out-of-game agreement with the DM), but ultimately even if they don’t, that just makes it a difficult suggestion to use, not an invalid one.
If you say your build absolutely relies on this one particular tactic and everything you are building towards revolves around 1. ensuring you’ll be able to do that thing and 2. capitalizing when you do it, then even your tactics can be part of the build. That might be as simple as just ensuring you can always grapple things no matter how big, strong, or magically-protected they are, to something as specific as the Black Tactica war weaver–counter-nuking build, to something as convoluted as a particular approach to Pun-pun ascension.
Your build includes all those details you feel you need to include in order to make the build function as intended.
Anyone telling you that any part of what you consider to be part of your build, is not actually part of what is covered by the word “build,” is quite simply wrong.