Frequent flyers: Is there a "best way" any more to fly into one airport and fly out of another?

Is there even any advantage to staying with the same airline?

My trip itinerary is a big triangle: fly from California to Florida, take train up the coast, fly from Mass. back to Cal.

I haven’t flown since 2012 and at that time didn’t even qualify for senior status. Now I could use some help with gate-to-gate transfers on account of foot injuries.

I don’t have to go for rock-bottom prices, but I am on a modest budget.

What’s your best advice for planning this tricky thing?

Thank you.

Tags as I wrote them: travel, air travel, flights, airlines, SJC, MCO, BOS, air fares, senior accommodations.