Congrats on getting into reloading.
-You'll definately want to tumble before resizing. Dirt and debris can scratch and clog up your dies.
-You'll want to check your case length once and a while and trim them once they've reached max case length. In a cartridge like the 40 S&W it will take quite a few firings to do so. I've fired some of my 40 brass 4-5 times and I still haven't had the need to trim them. I'm not loading mine right to the max so if your loads are hot they may need trimming sooner.
-Follow your dies instructions for crimping. You'll want to take the bell out from the case expander and then a little more. You should be able to feel a slight inward curve on the case mouth but not so much that the edges are rounded.
For my M&P 40 I've been using 180gr. plated bullets and 5.0grs of bullseye. It's not the first powder I'd recomend but I also use it for my 45acp in my bullseye loads for our clubs competitions and I hate having a bunch of different powders around.
I've found it to be quite accurate in my M&P but I've been told the powder is too slow for it and velocities are to low to make it suitable for IPSC.
I was also using titegroup but found it not as accurate and dirtier than bullseye.
