Energy refreshes are better than any store purchase.
You will get about 30% more of whatever you are trying to get by farming it off a node for the 50 crystal refresh cost, compared to buying it in a shipment. You also get all of the other stuff off the node (credits, ship materials, other gear) effectively as a bonus on top of that 30% more of the specific item. While below level 85 you are also getting more experience to level up faster.
You should be spending nearly every crystal you earn every day on energy. Your income slowly increases as you play, earning more rewards from more events. Work out what your budget is to have a slowly increasing stash.
I'd start with all 3 normal energy refreshes for 50 each per day, 150 crystals. Every account gets at least this if they do their dailies and gal war each day. Next I'd add a single cantina refresh for 100 and then a ship for 50, and alternate adding them. Once they are at 3 each, maybe start adding mod refreshes. Low level accounts struggle to have enough credits for both characters and mods, so that's why I'd leave mod until last. If you are in a guild launching raids every 3 to 6 days, credits may not be an issue, and maybe add mod energy slots in along with the cantina and fleet alternating build up. Remember, you do want a slow increase in crystal stash.
But don't blow the stash in the store. The stash is for when chase or bonus drop events come around, so you can get even more energy when those events are on. For reference, I'm end game, so my crystal income is vastly different, but even so, if I have less than 10k crystals, then I'd be worried i might not have enough crystals if a series of bonus drop events happens, like occurred in the second half of last year with the leia requirements. So I use 10k as my floor, and only when I'll stay over that, I might consider some of the Jawa daily deals. But only if they work out to ~20% better value than shipments for me.
You mention the faction and mega packs, and you'll note I have not. They are not worth mentioning.
