Well, first off:
Don't do stupid stuff for something shiny.
If you can't afford it, maybe just don't do it.
Secondly, both the banner and the orb offer are going to be here all january (or at least a large part of it) So if it's Gunnthra you want, you could always try to get her the free way first.
To compound unto this.
Before you do something stupid, check out what your expenses are for January, this bonus will be up until the end of January (or early February) and as such, you can wait until the later banners (RD or the LHB) to get the orb pack, so there's no hurry. Save monye, and be smart.
Secondly, try to get Gunthra the usual way, and maybe save the orb pack for the later half of the month and or the RD/LHB considering we're getting beast units (who may be very potent)
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes