i just started to get into shark fishing was just wondering what should my main line on my reel should be i was thinking 80 then a 125 topshot need some tips plz
I would either load it with 80lb braid with a topshot of 150 yards of 100lb mono or load it all with 50lb mono. I used 50lb mono and i haven't had any troubles with it, and mono is cheaper than braid.
You can ask 50 people and they will give you 50 different answers on this question.
A common thing seems to be 80 or 100 mainline mono (maybe bull buster) and 100 or 130 top shot
fill it with braid than a top shot of 100pound bullbuster or 80pound andes.youll get a lot more line capacity with the braid on the bottom! 
I have mine spooled with 600 yds JB Hollow braid and topped off with 100 lb Hi Seas Mono. We landed this 8'10" bull on it last Sept.
Is that Davin holding that tail rope Elwin? 
ive had my 9/0 for afew years and have 50lb bullbuster mono on it and love it. think it holds like 700 yds and have landed some nice sharks. also like someone said above mono is much cheaper than braid lol.
I do strait 80 mono on my reel you should get somewhere around 500 np and that's plenty for a 9/0 IMO if you want more line buy a bigger reel!