Which internet speed should I get: 3, 15, 20, 30 or 50mbps for my house? PLEASE HELP?

[Arnold]

We are using 1 wireless enabled printer ,two desktops , 1 wii ,1 xbox 360 , 1 smart tv ,1 laptops, 1 tablets, 1 ipod touchs, and 2 iphones for wifi at home.
Right now, we are using TWC 3mbps. My parents always say 3 mbps is enough, but it's keep lagging in games and I have good ping.

So which internet speed we should get 3(the same), 15 20, 30 or 50 mbps?

Thank you
My Dad try to fake that they can't afford it but they can, and my uncle told me they my parents are trying to fake it because it's the perfect for his needs. On the other side When I watch youtube videos in 1080p it is always buffering. When I asked my uncle he said it's not enough for me because I have lots of devices. I'm consider switching to verizon fios 50/25 or 75/35. On my bill I pay for internet and tv from Time Warner Cable for $59.99. For Time Warner Cable 15/1 mbps is $64.99 with tv, 20/2 mbps is $74.99 with tv , 30/5 mbps is $84.99 with tv , 50/5 mbps is $94.99 with tv, 75/5 mbps is for $104.99, 100/5 mbps is for $114.99. Or Verizon Fios which is available in my area. For Verizon Fios 15/5 with prime hd is $79.99, 50/25 mbps with prime hd $89.99, or 75/35 with prime hd $99.99. Is there a way to convince my parents to upgrade

[Fola]

For all that you definitely need more than 10Mbps

[PC Doc]

get the max speed

[juel]

i think you should 30 mbps