Forty years ago I started with a Lee handloader at the dinning room table and it worked for me.I now use a RCBS kit and load for about 15 different calibers all single stage, I also load 4 shot gun guages one at a time.I like the fact I have much better control over each load.
To answer your question -NOTHING- yes a kit will give you what you need to do what you want but I can tell you right off you will add to the accessories and before you know it the bench will be full of things that you will not use,but will have just in case.