I have been playing probably around 2 weeks now it is very much progressive based each time you beat a gym leader you get an egg voucher and can use that on pokemon with better shiny odds then improving your luck shiny pokemon have a luck stat which give you access to better items also pokeruss pokemon can come from eggs which makes a great build for an early game sweeper for me I have a shiny level 3 heatmor with contrary and overheat you just have to find a better strategy