I've never trimmed any straight pistol case. Trimming is for bottle necks, rifles.
Get an auto disk powder measure, SUPER way to go. I'd get the O press rather than the turret. The O press is pretty strong and will last. I'd save for a better turret later, one that's stronger built. I've been using a Lyman for 35 years. I'm sure I'd have gone through a couple of Lees in that time. You can always use the O press for sizing and other such stuff later when you get a turret. JMHO of course. The Lee will last long enough to get you into the game and more involved and knowledgable and it'd probably last until you decided to spring for a progressive, at which point might I recommend a Dillon.
Lee dies are of good quality. I have Lee, Hornady, and RCBS, all work well. I like the Lee dies for my pistol loads because I like using the auto disk powder through charger on the expander die.
I also bought a little Lee C press to use only with a Lee auto prime. I don't like the little cheesy hand tools. I wore one of 'em out rather rapidly. The auto prime used on a press will last a lot longer and it's also a lot easier on thumbs. I'd rather prime on the up stroke than downstroke as with the priming arm on the press.
DON'T put a roll crimp on the case! A Lee die, at least, will roll crimp your load if you run the bullet seating die down on it far enough. Press the nose of the loaded round into a hard surface with your thumb as hard as you can stand to. If you see the bullet seat in any farther, you need to buy a taper crimp die for the caliber and taper crimp it. The reason for this is the .45, like most auto pistol rounds, headspaces on the mouth of the case inside the barrel. If you roll crimp the front of the case, you'll have excessive head space.
Lastly, load a dummy round with no primer or powder to proper overall length. Set this dummy round aside and use it when you're setting up your bullet seating die. Put the dummy round in the press, lower the lever all the way, then back out the bullet seater and screw first the die down until it gets tight, then run the bullet seater down to the nose of the bullet. I keep a dummy round for each of my favorite loads for this purpose since I have several pet bullets for any given caliber.
Just some things off the top of my head. Get in a routine. Check all cases after the powder charge step and make sure the powder levels look the same in all of 'em. Check the primer of each case as you prime it by running your finger over it. Make sure you don't have any primers protruding from the case any (known as a high primer).
I could probably go on, but this is all the little stuff I've figured out the hard way in some cases over the years.
Oh, btw, don't go by that goofy chart on powder charge you get with the auto disk powder measure. Get a scale and weigh the charge you are about to use. The chart is usually off. It'll stay the same, just that the chart doesn't give correct charges in my experience. Once I get a load and charge weight I like and determine I'll keep it (haven't developed anything in a while) I write it down in my log. Keep good notes and note the bushing you are using for the charge weight. When you set up for that load again, all you have to do is go to the bushing size on your auto disk (I also have the Pro version). You won't have to weigh anything. I do check new powder once just to make sure it's not different from the previous batch, but that's it.
