This Ramadan was my first one and I broke the fast some days without valid excuse, only because fasting was very difficult this first time. I don’t remember how many days I broke the fast during the month.

1) Is it expiation required since it was my first Ramadan?

2) What do I do for expiation?

3) Do the poor have to be Muslims or can it be any?

4) Is it allowed to mix kafara? Like, if I fast two consecutive months and then only pay 500, or fast 4 months and pay 400. Or do I have to do completely one or the other?

1) Yes expiation is required since you are a Muslim and laws of Islam apply.

2) Try to estimate how many days you missed. You have to make up the days you missed and feed 60 poor people for each day missed on purpose without an excuse.

3) For the kafara most likely they have to be Muslim.

4) You can’t mix kafaras, but you can pay to feed people in poor countries where it is fairly cheaper.