A lot of people gave good ideas. So without a ton of details my thoughts summarizing some of the key tips plus one other idea for macro shooting.

Batteries: I have always used 3rd party batteries without issues. I agree they do not last as long as the original OEM batteries but getting 70-80% of the number of shots for only a quarter of the price is a great tradeoff. As someone else noted, all the batteries are the same for a particular model. Buy the ones that do not pretend their stock has more energy. If the OEM one says 1400mAh, most of the 3rds party ones will be around that as well. The one or two venders claiming their are 2000mAh are simply untruthful.

One tip is checking places like KEH.com for used stuff. They even sell used batteries. I wouldn't buy 3rd party used ones at all, but when they sell the original camera manufacturer batteries it might be worth a look. Also for small items, use their eBay outlet store because they usually sell eBay listed items with free shipping while the same item at their web site will be the same price but adds shipping. I recently tried a used Olympus battery for my Olympus camera at about $22 vs. $50 new. More expensive than 3rd party but cheap enough to give it a shot. So far that battery performs as well as my other Olympus battery.

Without picking any single model, as others have mentioned any of the faster prime lenses in the roughly 15-25mm range are nice to have for something different than zooms and also to allow shooting in lower light hand held without flash where an f1.8-ish aperture allows you a couple faster stops over many common zooms. Actual focal length is really a person preference so no one can tell you that 20 is better than 25 or 25 is better than 17. You have to figure that out for yourself.

Finally, my tip to try out macro shooting on the cheap. A blogger/youtuber named Rob Trek does really good video on m43 equipment, techniques, flash use, etc. This one is very good at demonstrating the type of macro shots you can get with your current 40-150 "R" lens and a couple of $23-ish extension tubes...

https://www.youtube.com/watch?v=Xhxche-R1aY&feature=emb_logo

For $23 is it a no brainer to use as a start to see how you like it. Later if you find you want to keep going then you can look into some of the dedicated Macro lenses such as the Oly 60mm. But if you lose interest then you only spent as much as a decent bottle of wine.