Clipless, don't worry about anything else, you are holding the bike back not the other way around.

Then maybe after you really start riding a lot, just get a whole new bike. That bike is not really worth upgrading.(clipless pedals can always be transferred)

And don't worry about bike weight, it really won't make a big difference.
My bike weighs ~20lbs and I am faster than some people with sub 15 lb bikes, and I know some people who are wayyyy faster than me even when riding their 20 year old steel mountain bikes.