Personally I would recommend a gas check design, at least for the .30/30. Pick one from a major mold maker in the 150-170 gr. weight range and you won't be off much. If I had to recommend just one for starters it would be the old Lyman #311291. With just one mold, make it a gas checked one IMO. You can run it slow or fast, but a plain base bullet you can only run slow. (Overly simplified, but that's the gist of it.)
Slug your bore before buying any molds and bullet sizing dies. It's really easy. Push a soft lead #00 buckshot (or soft lead .32 pistol bullet) through the bore and then carefully mic it. Rule of thumb, size .001-.003" over groove diameter (not bore diameter-which is the top of the lands). The exact size will be dictated in the end by your particular rifle's demands, but it should fall within that range. If you really want to get anal about it, do a cerrosafe casting of the neck/throat area and select a bullet shape that allows for a perfect fit in the throat. Save that for later and just get a common .30 mold and size it a couple thousandths bigger than the bore and you'll be off to the races.
I'll let someone else talk .38/55's- out of my bailiwick.
