Alloys -- Go for silver colored multi spoke max 8 spokes or 5 spokes alloys.
Tire Size -- stock size is 155/80 R13, best upgrade is 175/70 R13. Anything more will kill the little i10. Go for Turanza series if bridgestone, yokohoma a drives or michelin XM1+ or XM2. However there is a news that current XM1+ is not that good.
I own i10 auto asta. I am also considering plati alloys, however will wait for more 5k kms.
K&N or green cotton, iridium spark plugs and FFE would be sufficient. Also do let me know your fuel efficiency.
The 1.2 mill of i10 is not a mod friendly unit in first place. As suggested above max you can go for is a K&N filter and a FFE but that too might give you just a couple of bhps more. I'd suggest you a matte finish bonnet with angel eyes in front smoked headlamps with led smoked tail lamps.
This will increase the sound however due to the free flow exhaust , your car performance and fuel efficiency will increase, of course that depends on the fact that you rev the engine or not. Hyundai engines tend to consume more fuel upon revving. You will feel the difference in the performance once you install them.
Buddy, tried a few mods on a friend's car and the results were not that tempting. So, just speaking from my experience. We tried, bigger throttle body, complete head job, K&N, FFE, iridium spark plugs, high power cables and even tried a ECU map but didnt got much gains in power/performance.
The latter is a bit wider and so would have a better grip. Both would have almost the same speedo err so not much issues in that area. I'd suggest you to go for 180/60 if you do a lot of highway drive or drive a bit fast as it would give you much better grip than 175/70. BTW, have you decided on any brands?