Tomorrow my sister & leave for London/Paris. We fly form DFW to London Gatwick and want to transfer to Waterloo for our train to Paris. We've allowed several hours so as not to feel too rushed. In looking at the Tube journey planner website, we can take the First Capital Connect to London Bridge

Oops - posted too soon
London Bridge connecting to Waterloo (East) on the Southeastern.

Easiest & cheapest, hasslefree carrying our suitcase & carryon?

See janis' comments on your other post. First Capital Connect is a commuter train and you're arriving during a Monday rush hour.

Don't

Why not take Gatwick express to Victoria and then go to Waterloo from there?

Thanks to fellow posters - I just bought the discounted (50%off) Gatwick Express tickets online & it worked like a charm...

Have a great trip and post a report when you get back. My sister and I will also be taking our first trips to London and Paris this May.

A little too late for dorkforcemom, but...

a few intrepid travelers have taken Southern Trains from Gatwick via Tonbridge to Ashford International and picked up the Eurostar there. A Southern DaySave ticket will transport four adults for £20.

This involves a certain amount of schlepping, judicious choice of Eurostar trains (they don't all stop), and is definitely not for the faint of heart.

Just as well dorkforcemom has already bought his tickets then!!!

<<< Why not take Gatwick express to Victoria and then go to Waterloo from there? >>>

Because OP then has to either get a taxi or negotiate the Tube with luggage including a change from the District to Jubilee line - which will still be busy with commuters