In my opinion it’s best to focus on the arc right away instead of combat GBs. GE is easily negotiated if you have a few goods buildings or do recurring quests. It’s best to get the arc to 80 as soon as possible in my opinion, so leveling other GBs before it, even if you aren’t making a ton of FP per day, is a waste of time that you could be sniping to get massive amounts of FP. Combat GBs can be much more easily leveled once you have a level 80 arc and a few level 70+ FP producers (Cape, AO, etc., but that’s a different discussion).
With that being said I would advise you to work on your arc now. Especially if you can already finish GE. Get that thing to 80 and do what you want from there, but trust me, I wouldn’t seriously level any GB until you have a level 80 arc. Many people would tell you to possibly wait until your FP production is above 75 or 100 per day (I don’t know what yours is, I’m just throwing this out there), but I don’t advise waiting for anything. Even if you only make 45 FP per day or less I would still tell you to work on your arc. Unless there is suddenly a more profitable place to spend your FP, but until your arc is at level 80 I doubt that there is. FP production will increase as you go, so don’t let that hold you back from leveling your arc.
How to level the arc? I would advise, most importantly to get in a guild with a 1.8 or 1.9 thread. For the first 15 or so levels swap FP with other players who have arcs at about your arc’s level (Don’t use guild swap threads. Find private swap partners so you can always get the rewards). After that put FP in your own arc. You can still swap FP, but don’t swap as much as before. Putting FP on your own arc at this point makes spots lockable more quickly. Then, when first and second are lockable for the rate of your guild’s GB leveling thread (usually 1.8 or 1.9), put your arc into the thread and your guild mates with level 80 arcs will lock the spots for a ton of FP. They won’t lose any FP, because the contribution bonus on their arcs is so high. Above level 30, your arc will practically self level. Because of your level 80 arc guild mates you will most likely achieve about a level per day. At this point use FP packs to snipe for the blueprints you need. Above level 70 it becomes harder again, as you will need to put in more of your own FP to make spots lockable, but you should be so powerful at sniping at this point that levels 70 - 80 will go fast.
Here is a link to the arc calculator tool that tells for you how much more FP you need to spend for spots on your arc to become lockable:
https://foe-tools.github.io/gb-investment/The_Arc/
So for your current situation I would advise focusing 100% on your arc until it is at level 80. Especially if you can already do all of GE, this is definitely the most profitable thing to do. Once you accomplish that, I would focus on either power leveling FP producers or power leveling Chateau Frontenac. In your case I would recommend moving on to CdM after the arc because you already have it and are working on it now.
Well in any case I hope this was helpful to you... GB decisions are always hard!
Happy Forging and good luck with whatever you decide to do!