Do not confuse "the first order" of being something new than the Empire - they are part of the remnants, multiple factions spread across the Galaxy and just happens to be the one where this Snoke decided to lead and turn in to a leading force in order to restore the Empire in its new glory.
The battle of Endor is not revealing what really happens to the entire Empire Fleet - the thing is that the Galaxy, the systems under Imperial control, are governed by "Moffs" (like Tarkin) who are like supreme leaders of a certain Imperial Fleet and Planet(or planets). So, just because the movie represents the "first order" as main villains doesn't mean they are alone nor weak. They were part of the Empire, their fleet might possibly be lead by "Snoke" who was a Moff Snoke (or using other name, where Snoke is nickname). Maybe they were participating in a battle similar to the imperial fleet in Jakku and there he got so damaged(read wookipedia about the story of captain Cree - her star destroyer Inflictor is the one we've seen from trailer and in the movie).
Overall - the first order are not weak nor resource-less...they build starkiller base and proved to have a huge army placed on it on top of a fleet (which we might definitely see in 8th movie, possibly Snoke is there on some kind of super star destroyer etc). In New Hope we barely witnessed the Imperial Fleet and we saw part of it at 6th movie and even then it was meeh (cuz they were ordered not to fire). So speculating that they are weak only cuz we saw 1 "new" star destroyer is not right. We all know star wars is 30% movie and 70% background information about the movie coming from other sources (primary wookipedia).
You know that after battle of Endor all Moffs formed alliances with one another in order to prepare an attempt to counter the Rebels. Some Moffs decided to go alone (with their fleets) and establish new groups, similar to the First Order. Thrawn had a huge armada, just like Pantheon but all that we know from wookipedia and comics/books etc. One movie - the 7th - was not enough to represent the huge potencial and resources of the First Order, so the best way to see if they are strong is to use what we've seen in the movie:
1) They have very good spies, almost instantly leaking information about the rebel movements (first part of the movie, later in Maz Kanata castle and in the end HOW did they knew the location of the Resistance? Definitely someone told them that. There was no Princess Leia interrogated by Tarkin to say they were at Alderaan and later Yavin...)
2) They have superior technology than the Empire, better ships and far more skillful pilots and troopers (finally)
3) They have resources enough to build starkiller base (the symbol of the order all around it proved that its their property...no need to discuss it - its their base)
4) They have the only "alive" possible candidate to be called close to a SIth Lord (Snoke) and apprentice as Vader (Kylo)
5) They have something far more worst to offer and the loss of starkiller base was not so much of a loss to them - THAT we saw in the eyes of Snoke when General Hux went to report the failure and the imminent destruction of the base - he simply said "Leave the base at once and come to me with Kylo Ren. It's time to complete his training." - it was like "Fak the base man lol, bring me Kylo to make him a badazz".
So don't conclude they were weak. If you ask me they were far more brutal and their actions caused far more destruction in 1 movie compared to the Empire in 3. They knew where to strike the New Republic and they did it swiftly. They are fanatics lead by someone which possibly is super angry and evil but we shall find that in 8th movie cuz in this one we saw nothing more than that "this" dude thinks of himself of being someone "superior" - the oversized hologram..."supreme leader" title and etc...definitely is someone they trust to lead them to glory. Hope his story is nice.