I'm renovating a kitchen. It has a range top and wall oven, both get power from separate double pole 30 amp breakers. I will be adding a 50 amp breaker for a new stove, and also reuse the wall oven on the existing 30 amp circuit. I recently had a new 200 amp service panel installed. All the circuits in this 1950's ranch were joined in a junction box above the new panel and the goal is to rewire and add circuit as I renovate each room. There are currently 2 15 amp circuits that power the kitchen and also branch off into the basement. I will rewire these 2 circuits back to that junction box and use one for the basement lights and one for the kitchen lights. The rest of the kitchen will have 3 20 amp circuits, one for the frig, one for the dishwasher and disposal and one with a ground fault receptacle for the counter outlets. I have a smaller panel box with 10-20 breakers in it that I picked up at a yard sale, only because they were the matching breakers and I was going to just use them in the new panel, however, now I'm thinking I may just wire the new 20 amp circuits to this box and use it as a sub panel powered temporarily by the double pole 30 amp existing breaker, then late change that out to a 60 amp late so I don't have to keep working in the main panel. I know the 30 will not power the 3 20's, or at least I don't believe so, but during renovation none of these will be used other than to test them one at a time, I could then swap out the breaker in the main with one big enough when the time comes. Any help hints etc, much appreciated. Thanks

Your 30A breaker that you want to use for a sub panel feed probably only has 3 wires... if you are going to do a 220V subpanel then you will need 4 wires. (Leg A , Leg B , Neutral, and Ground) where ground is connected to the case of the subpanel and the neutral is connected to an isolated neutral bar in the subpanel. Whether you can change the breaker to 60A later depends on the gauge of the wire from the Main panel to the subpanel. Don't recall but believe you would probably need 6 Ga to feed a subpanel with a 60 A breaker. Also, check your local code for the minimum feed to a subpanel.

The subpanel will be within 15', I guess changing the wire and the breaker now make more sense, I'll only have to go into the main once. Should I just go with a 100 while I'm at it and allow for any future needs. Thanks

If you're going to be running wire anyway and you can get to new 200A box without much difficulty... that's what I would do. I'm not a licensed elcectriction... but my opinion is that you should do a sub primarily when capacity or distance to the main is the biggest issue and I'm not too sure I'd put much value on distances inside 100' or so if they are within the same structure. Going with 100A sub panel may cause you some future grief if you're trying to find a 100A breaker to feed your subpanel from your existing main. I've never tried to find one that large but suspect it may be a more rare and expensive thing but you may want to check that out before you commit to doing a 100A sub.