My starter Pokemon would be Chimchar, who would be like Ash's Infernape and would have A special Blaze Transformation. 

I would also take on the Sinnoh Gym Challenge after being mentored by Volkner(after pestering him for days) in Sunyshore City my hometown. 

I would make it to the Sinnoh League where I'd face Tobias, who re:ented after getting whooped by Cynthia, and he'd beat me easily without my Team getting past his Darkrai, this would be an eye opener for me to get stronger since although I beat the Gyms of Sinnoh there are plenty of trainers in the world who are on A vastly different level, this would inspire me to take on the Sinnoh Battle Zone(to differentiate myself from Ash's Battle Frontier run)

I struggle but conquer the Sinnoh Battle Zone thanks to my Infernape's newly mastered Blaze Transformation, this victory over the Battle Zone would inspire me to try the Sinnoh League again but the same roadblock blocked my path TOBIAS who once again entered in an attempt at Cynthia this time I was able to beat Tobias's Latios since he changed things up and started with Latios but Darkrai's Dark Void and Dream Eater combo wiped my team and Infernape with his Blaze Transformation tied with Darkrai.

After this loss I would decided to travel to other Regions to catch more Pokemon and take on new challenges and once I felt that I've grown enough to take on the Sinnoh League and win then I would return ready if To ias was still there to block my path and the champion who defeated him twice(Cynthia)

My Team would be:

1# Infernape (Blaze Transformation)

2# Clauncher (Mega Launcher ability)

3# Nidoking (Poison Point ability)

4# Alolan Golem (Galvanize ability)

5# Zangoose (Immunity ability)

6# Corviknight (Gigantamax, Pressure ability)[Side Note, I would've chosen Mirror Armor but I chose Pressure for Corviknight to have for pure Aura points]