Mac client taking forever to start, and also randomly crashes just after champion select

When I open the client, the league logo pops up on the screen. Then sometimes it says "another version of the client is already running" when its the first time I've opened it in the day. Once I hit either cancel or ok, it sometimes crashes automatically or crashes a long period of hanging. Also, sometimes the processing cursor comes up if I hover over the logo and it starts in about 3 minutes which is considerably long time.

Plus there are also random instances where the client hangs after champ select or just as the game is about to start in team builder. I've been placed in low priority queue many times due to this issue. This problem has persisted since patch 5.9 but has become much more evident and frequent now.

SPECS : MacBook Pro Mid 2010 version OSX 10.10.5 4GB 1067 MHz NVIDIA GeForce 320M 256MB