Agenda Help!

With 14 days I would pick two of the countries. Since you are flying in and out of Frankfurt, I would visit Germany and one of the others, and use trains to get around. It is difficult to recommend what to see without knowing more about your interests. What types of things would you like to see and do? Cities, small towns or countryside? Are you interested in history, art?

Before we get into the sights to recommend you see based on your interests (no one knows what you are interested in and what you are going to like) you should narrow down the countries to visit. I would cut out and save Luxembourg for another trip.for logistical reasons.
Based on the day you said 14 and the countries Here is a rough draft agenda
Frankfurt to Paris on the plane. Stay 4 days.
Take train Paris to Antwerp or Brussels 4 days. Visit Ghent and Bruges on day trips.
Antwerp to Amsterdam spend 3 days
Fly back to Frankfurt for 3 days include a Rhine Valley Trip from Frankfurt with a Rhine River Cruise

Let us know what you think

Day 1. Arrive Frankfurt Airport.
Train (50min) to Cologne (1 night)
Day 2. Train (2hr 45min) to Amsterdam (3 nights)
Day 5. Train (1hr 30min) to Antwerp, Belgium (3 nights) with days to Brugge & Ghent
Day 8. Train (2hr 15min) to Paris (4 nights)
Day 12. Train (2hr 15min) to Luxembourg (1 night)
Day 13. Train (2hr 25 min) to Koblenz, Germany (2 nights) with a day on the Rhine
Day 15. Train (1hr 10min) to Frankfurt Airport

"Right when we get to Frankfurt, I am thinking of hopping on a flight to different country right away"

Before you do this, be FULLY aware of the risks and complications. Here's a good primer: https://www.tripadvisor.com/Travel-g41707-c207311/Newton:Massachusetts:Connecting.On.Separate.Tickets.html

Similarly, unless you have a VERY high tolerance for risk, you will want to be close to Frankfurt the night before your flight home. If anything happens and you miss that flight, you have to buy a new, one way, last minute ticket home - potentially very expensive.

Don't think countries - think destinations within the countries. For instance, Frankfurt to Paris is only 4 hours on the train; Frankfurt to Strasbourg (for Alsace) is a bit over 2 hours; but Frankfurt to Bayeux (for the French Basque Country) is 7-8 hours. So, starting in Frankfurt, some parts of France are much easier than others.

You will not want to be moving every day (trust me on this), and you probably don't want too many long train rides. What to see will depend on your interests.

Trains will be the way to go on a trip like this. To find train times and connections for most of Europe, and prices for trains that start or end in Germany, use the Bahn (German Rail) website http://reiseauskunft.bahn.de/bin/query.exe/en, following Rick's tutorial: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules

To get the cheapest tickets, you'll want to buy in advance, if you can work with non-refudnable and non-exchangeable tickets (or tickets that severely limit these actions). Here's a handy list of where to look for these, from rail guru The Man In Seat 61: http://tinyurl.com/bo8x6o6

If you're not seeing train connections, you can try looking on Rome2Rio to find out how to get between places: https://www.rome2rio.com/. Note that the prices and schedules on Rome2Rio are not always accurate - always double check with the actual airline, bus company, etc.

David's itinerary is a good start. Look into the places he lists - do they interest you or not?

It doesn't make sense to land in Frankfurt and immediately fly somewhere else. Since Germany is on your list, you should pick your first city to tour somewhere close to Frankfurt. Since you'll be likely jet lagged, it's better to "ease" into your trip instead of making an aggressive back-to-back flight schedule that needs to come off without a hitch.

Using countries as a planning tool is way too broad, especially when two of them are very large. You need to focus on the smallest units when planning. Start with particular regions, cities, or sites/attractions that interest you. Then use those to string together an itinerary that minimizes travel time and distance. Fourteen days is not as much as you think, especially if you are including the landing/departing days in those 14 days. Look at some of Rick Steves tour itineraries for examples, and assume that a do-it-yourself tour will be much less efficient and cover less ground in the same timeframe. Think really hard how many hotel moves you want to make during those 14 days.

Hello Etta_Ball. Will you be away from your home a total of 14 days ? If yes, you will be at Europe a total of 12 days, including the day you arrive at the airport of Frankfurt.

Hi,

If you're flying into FRA and connecting relatively soon afterwards, I would suggest Budapest or Vienna. I've flown from SFO to FRA nonstop, then within 3 hrs after Immigration and baggage claim was on the ICE train dep from Frankfurt Hbf to Vienna via Munich. Of course, I didn't arrive at Wien Westbahnhof with train delays, etc until 2330. That was a long day. Another time it was Frankfurt to Berlin within a few hours of landing. Unless you're getting a deal flying into FRA instead Paris CDG or you find CDG disagreeable, then I can see why flying to FRA, then leaving right away for Paris. Understandable. A good woman friend of mine always flies to CDG, then connects, if need be. Keep in mind you could have jet lag when arriving at FRA, but then not everyone is jet lagged upon arrival.

You are flying in/out of Frankfurt and you want to see Paris. I would say spend a couple of nights in the Frankfurt area (take a train the day you arrive), then fly to Paris for as much time as you want to spend in France, then return to Germany (perhaps spending a few days in Belgium or Amsterdam) and spend your last night in Frankfurt before you fly home.

I suggest this.
Day 1 Stay in Frankfurt and recover from jet lag. It is an easy city to stroll through. Not too much to see, but you'll be tired anyway.
Day 2 Fly to Paris early, spend day in Paris. (if you use a cheap airline, you'll probably be flying from Frankfurt-Hahn airport, not the main one, so allow yourself time to get there.)
Day 3 Spend Day in Paris
Day 4 Spend Day in Paris/ go to Versaillles
Day 5 Train from Paris to Ghent. Consider Flixbus instead of train. It's like 10 euros for the whole ride. About 3 hour trip. Includes wifi
Day 5 Visit Bruges (20 minute train ride from Ghent). Stay the night in Ghent or Bruges. They are both great. I prefer Bruges. You could replace these with Brussels, but I don't find Brussels to be worth it. Just my opinion.
Day 6 Take Flixbus from Ghent to Amsterdam. It is a 2 hour bus ride. You could take the train but it is MUCH more expensive. I'm a student on a tight budget so I prefer the cheaper option but that may not be your situation.
Day 7 Spend in Amsterdam
Day 8 Spend in Amsterdam
Day 9 Spend in Amsterdam. Consider day trips from Amsterdam on any of these days. Holland has a lot to offer.

Now for Germany
If you are in to history, especially WW2 or Cold War, I suggest flying to Berlin on Day 10 and spending a few days there.

If you are looking more for German culture, I suggest taking the Easyjet Amsterdam-Hamburg flight. Its only a 30-minute flight. Very Cheap. From Hamburg, you are 30 minutes from Luneburg and 30 minutes from Lubeck, both beautiful old cities that were not destroyed in the war.
From there you can work your down the Rheine back to Frankfurt. Cologne is worth checking out if you have time.
Personally, I don't think Luxembourg is worth it. But it is pretty close to Frankfurt, so you could take the train from Cologne to Lux City if you really want to see it.

This is what I would do, but everyone's different.
Hope this helps
Cheers