Blaziken is not legal for VGC, as well as all non native Friend Safari pokes. If you want to use Kangaskhan, I would focus on a defensive build with scrappy. To partner up with it, I would use a lead that can setup dual screens. Perhaps Klefki.
Kangaskhan
Nature: Adament
Ability: Scrappy
Item: Mega Stone
EVs: 90 HP, 172 ATK, 124 DEF, 124 SDEF
Sucker Punch
Return
Fake Out/Power-up Punch
Protect
This build is to work with Klefki as its the supporter for the team. You want to pay attention to your opponents team during the preview. If you see any common threats like spore or sleep inducers, you want to lead with Kangaskhan and Klefki. Kangaskhan is pretty bulky with the def EVs so you wont have to worry about it going down in a single round. You can mega evolve and then go for the power-up punch to get the +2. After that you can either sucker punch or return things at +2 at 150 percent damage. You can also mega evolve and go for protect to give Klefki a turn to setup screens or status. Its EV spread is for VGC so there are really no hard number. The def EV will work well with the screens when you mega evolve, putting either def stat about 200, which will increase its staying power.
Klefki
Nature: Impish
Ability: Prankster
Item: Leftovers
EVs: 252 HP, 126 DEF, 126 SDEF
Safeguard
Light Screen
Reflect
Thunder Wave
Im not a huge pro with Klefki but it is a really good poke for doubles in my opinion. Its ability prankster allows all status type moves (attacks that dont do damage) to go first as they all get +1 priority. Depending on your opponents lead, you can setup either screen (this depends on your knowledge of common attacker builds) For example, if you opponent leads with a Goodra and Gengar, you can assume 90 percent of the time they will be special attackers so setup Light Screen. If your opponent leads with a status inducer, you'll want to use safeguard right away to prevent the sleep, burn or paralyses, which will take a turn from them and allow you more setup. Thunder Wave is to allow your sweepers to easily outspeed threats your opponent may have and having a Kangaskhan at +2 being faster hitting for a neutral Return can cripple your opponent. Between using protect and thunder way on key turns, you'll have no problem winning.
Just keep in mind electric Pokemon can no longer be paralyzed. Another Pokemon that will pair well with them is a Pokemon that can use heal pulse. It allows you to heal one of your teammates if their health is getting low. There are a number of good Pokemon that learn it that can be used in VGC. I hoped this helped.