My current build for Xbala in arena mode, it's sort of a hybrid build leaning on attack speed and utilizing his intrinsic power boosts from his passive and bolas to make him pack a wallop end game (crits in the 5-700 range).
Transcendence - I see a lot of Xbala builds that don't run trans, or build it later in the game and I think to myself "are people not realizing how strong this is" especially on Xbala. Let me put it in numbers for people, just equipping transcendence gives you a 72.8 increase to your attack power, no stacks, nothing else, its hands down the most powerful item he can equip. Once powered up it'll give you 750 extra mana which translates to another 22.5 power and allows you to have bola's up almost indefinitely (this is a good thing, get it early, stack it early).
Ninja Tabi - I prefer them to warrior's for the attack speed and I don't really notice the 20 points at endgame.
Asi - Standard hunter as/pen/ls item is standard and gives decent sustain while letting you hit tankier gods a bit harder.
Qin's Sai - Gives you more power, increased attack speed and bonus damage on basic attacks based on your enemies max health.
Hastened Fatalis - While not as powerful as some of the alternatives in the 5th slot, I have a soft spot for the attack and mobility speeds this provides allowing for kiting/chasing without using your escape.
Deathbringer - 50ap/20%crit and when you do crit it hits like a truck, if you're building any 1 late game crit item and can afford it based on time left in the match this is the go-to to bring the pain.
Alternative - replacements for the 5th slot include titan's bane/Ichaival for more pen against tankier groups, bloodforge/soul eater to help deal with assassins and warriors that like to pick on you, and really anything you could use in a niche case (build nemean once against a group of 3 hunters and 2 ***. to great affect).
Dead of Night -passive- God kills grant a permanent 5 physical power boost stacking up to 6 times totaling 30 free power (getting early kills to power this up will pay off in the mid game letting you power through enemies when transcendence is powering up, just don't get yourself killed going after them)
Branching Bola -toggled self buff- Causes your basic attacks to hit for 10/20/30/40/50 additional damage, and causes them on hit to split into 2 that then travel up to 30 units behind target and deal 30% damage to enemies hit (but don't apply on hit effects). The bread and butter of this build, I personally think if your not building transcendence and maxing out this skill first then your using this god wrong. A toggled selfbuff for +50 and makes my basic attacks aoe without having to buy an overpowered item (trans aside) is ridiculous and makes you a constant threat. Costs 8/10/12/14/16 per shot but this is negligible with the 18mp5 you get with trans, just don't shoot at empty space for no reason.
Poison Darts -cone damage attack- Fires 10 darts in a cone in front of you dealing 30/45/60/75/90(+40% phys)damage with each one. Enemies can be hit by up to 3 of the darts with the additional darts dealing 30% damage. Enemies hit by the darts are poisoned and take 10/15/20/25/30(+10% phys)damage every .5s for 3s and are slowed by 4/8/12/16/20%.
costs 70/75/80/85/90 cd 18/17/16/15/14; Useful to tag damage on enemies or as a slow for engaging/disengaging/saving a team mate being chased/setting up a combo with his rising jaguar ability.
Rising Jaguar -dash attack- Rush forward and jump into the air firing darts at all enemies in a 30 unit radius beneath you for 80/130/180/230/280(+20% phys)damage. Any enemies that you hit with it that were poisoned by your poison darts take an additional 20% damage. costs 60/70/80/90/100 cd 16s; While technically a dash attack meant to be combo'ed with poison darts, I usually save that functionality of it for late game once my power is built up and I can either guarantee it'll kill a god or they'll succumb after 1-2 basics after the hit. Early game always save this as an escape (although it doesn't work while you're under a slow effect and you only dash 30 units in can definitely save you in a pinch), I've died so many times using this as a chase early game I can't stress enough how underwhelming it is at that function til late game (or a guaranteed kill in the middle of the map, don't use it if it'll put you next to the enemies base without a way to escape).
Darkest of Nights -area auto attack- Each of your enemies is shrouded in darkness blacking out their screen to about a 10 unit radius for three seconds. During this time your basic attack range is increased by 40ft and your movement speed is increased by 20/30/40/50/60%. At the end of the darkness any moving gods are stunned for 1.5s
cost 100 cd 90s; I never really notice the distance increase from this (ranges in descriptions are typically inconsistent as are their translation to game play), but the speed increase is big, like having an extra sprint relic for yourself and the blackout really messes with enemy gods forcing them to stop or retreat in most cases. This can be used from anywhere on the map and will hit all enemies, and can used to engage a push or be used to save yourself and teamates being chased.
Get rank 2 towards transcendence right off the bat then save another 1100 and buy it first, its a huge power boost and getting it early means getting it stacked early and making you hit really hard midgame.
In the beginning stay with your group and pick off gods if an opportunity presents itself to do so safely. Until you get asi try to avoid 1v1's as your sustain doesn't exist so you have to be careful you don't get overwhelmed (2v1's will get you killed if you get stunned at all).
Once you have Qin's Sais your typically at the midgame and can start beranching off to take out gods on your own, anything squishy like other hunters and most mages will succumb pretty quickly to a focused assault (if you can keep them at a distance most assassins can be dealt with or at least averted). Your 5th item slot is flex and I run fatalis for as and mobility but titan's bane is a good choice for bolstering your damage against warriors and tanks, and blood forge can give you move sustain and damage against enemies like thor, freya and ao kuang, if you want more sustain without sacrificing attack speed you can use soul eater. Build what will best help you given the opposing team make up.
Once your in late game you're building deathbringer for all the pain it shall inflict on your enemies (seen 700+ crits with damage camp buff endgame). At this point its time to bring the pain, you should be doing tons of damage per hit and your abilities should be used to push when possible utilizing your poison darts/ rising jaguar combo to rip apart squishies. Be mindful of getting teamed up against and get help from team mates when needed but you should be able to dance around your opponents till they die just make sure your attacking someone for your life steal sustain (I've gotten into 3v1's and will kill 2 of them before dying to the 3rd).