Ironically, I played X-Overd for maybe a week or two total a while back, so i actually have semi-leveled characters and stuff. 600 eggs in one evening. So yeah, there's plenty of time.

I'm far from an expert at it (I stopped playing it after all), but for anyone having issues, here's a few tips:

1) The dark-element maid lady with boxing gloves, Veronica, is your tank. She's a freaking brick wall. Do *not* underestimate her - use her, love her. She has a move, "Ignite", which taunts every enemy on the field... and it almost seems as if the taunt persists for the rest of the stage, as far as I can tell. I don't think she does much damage, so just use "Ignite" every single turn possible, and the rest of your team will be untouched until the boss (as the boss can use AOEs). By the time you're at the boss, you can stop using "Ignite", and instead use something else to mitigate damage (as I don't think I've seen the boss hit anyone but her aside from AOEs, the "Ignite" effect seems to persist). Like the defend command, or the "Barrier" skill, or such. You want her alive and kicking as long as possible, to protect your damage dealers.

2) For the most part, the damage dealers can just use their 0 MP attack all the way up to the boss stage, to conserve MP. Veronica generally takes all of 1 HP damage per non-boss attack anyway, so there's no rush if you're struggling. Once you hit the boss stage, a decent strategy is to use your first turn to cast a "buff your attack/crit rate for a few turns", and then just cast your largest (L > M > S) single target skill every turn thereafter. Do note the elemental wheel - it's displayed on the battle screen, but as all the enemies in the egg stages are either light or dark (which are both super effective vs each other), there's not a whole lot of strategy there. You can mess around with the attacks that also have status ailments, but... I prefer just hitting things. Costs less MP. Maybe that's just me.

3) At some point I had that light-element healer lady, but I don't anymore. Wasn't using her that much anyway (due to Veronica), and her heals were prohibitively expensive. So she ended up just lightly bopping enemies every turn... which felt like a waste. So I just have 3 damage dealers, and a fourth who can debuff enemy attack and defense (seems to be random if it works or not).

4) If you can make it there, the egg stage 7 (called "Not Waiting Too Long", the 20 stamina one) seems to be pretty decent for farming. Each chest drop gives 15-18 eggs, and you're guaranteed at least one chest (sometimes up to 3 or so, if the RNG stars align). I struggled to beat stage 6 myself on manual, and barely failed to beat stage 8 (yeah, I suck, what of it)... but I can clear stage 7 on full auto, with everyone using normal attacks (except for Veronica). For whatever reason it seems like 7 is unusually easy, for its position. So if you're having trouble, see if you can manage to get up to 7, as you might find it easier.

5) Side note: When you level up, it doesn't just fill your stamina to full, it actually gives you your max. So if you were 25/50, and you leveled up to a new max of 52, then you would have 77/52. Which... is actually a quite nice way to handle things. You don't have to worry much about "using all your stamina before leveling up", as it's not wasted.

There's all sorts of other stuff, like equipment and the jobs and yadda yadda, but... eh. I'm sure other people could explain that better anyway. Good luck to anyone hunting eggs!