Peripheral Upgrade Priority

Jan 15, 2019
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I was given a gaming pc in the fall of 2018. I'm not sure which peripheral to upgrade first. I was given a generic membrane keyboard made by acer, my headphones are Bose sound true around the ear headphones, i have an eBerry usb mic, and an older 1650×1050 60Hz monitor. I'm looking at upgrading to the HyperX alloy elite mechanical keyboard, Sennheiser Game One headset, and the acer KG241Q bmiix 1920×1080p 75 Hz monitor. I can't decide what to upgrade next, any tips?
P.S. my mouse is a Logitech G502 and i'm happy with it for the time being.