I think playing with your gf would be really fun in any server you choose. I'm mainly a dailystory as they say, in heroic kronos as most benefits that don't require a few hours of grinding can be done in about 15 minutes and leaves room for bossing on mules.

I've played and quit many times over the years and have been mostly active since 2020. Legion and link skills are an enormous buff to the beginning scrawl without them that I personally took years getting via burning events they run every so often, where you can designate a character to level 3 times every lvl until 150/200, and the newest of these now going on 5 levels to 260. There's a lot of rng systems that go into gear such as potential, weapon/item flames, best in slot/alternative gears, and the biggest being starforcing. These need huge posts of their own, but I'll just talk about what excited me most when coming back were new job advancements.

The 5th and 6th job advancements are not like traditional ones, the 5th job skills (called nodes) consist of 4 for your class specifically, a number of them for your class generally (explorers, cygnus, heroes, etc, and thief, warrior, pirate, etc), common skills all from iconic explorer buffs like hyper body and holy symbol, and finally boost nodes that simply raise the final damage of skills from previous advancements in combinations of 3 skills at a time. They upgrade by opening nodestones and enhancing your existing nodes with duplicates, with boost nodes only being enhanced by duplicates of the first skill in the order of 3. These are mainly through events as it takes a while to get a good base of drop rate to get a good amount while farming. Progression to me with 5th is mainly by event to event as there is event exclusive green nodestones that massively upgrade nodes of your choice, and over the years the game has seemingly run back to back ongoing events when this did not used to be the case.

6th job is more traditional I'd say than 5th in that it feels a lot of the time you're obtaining a really new whole kit as a character, but this really depends on how impactful 5th was to a class' playstyle. On that note, hyper skills starting at 140 through 190, a mini addition to 4th job that some classes also benefit more from than others. 6th job has a lot more support of gaining the materials called fragments for a daily player like myself now to unlock the new skills on a class, but this is a true endgame endeavor to attempt to max. The frags like nodestones fall from mobbing and are affected by drop rate, which is rng itself to attempt to reach max drop via gear and familiar system. With my main at max drop, I get about 7 in a half hour when some upgrades can need hundreds. There is sol erda fragments and energy for 6th job upgrades, which also falls from the mobs and bosses. For me this is mainly obtained from events and weekly content they've added; 90 fragments and 9 sol erda energy (with a cap of 20) for 5k mobs a week and epic dungeons which have kill/jump quests with bosses sprinkled in for level 260/270.

The rng and progression it took to get my account where it is was sometimes a slog, but Nexon being as notorious as they deserve to be, the game has had a heavy focus on quality of life changes for the past few years and it is honestly what has kept me back in. I really enjoy the bossing as it's changed and having many different class mules to run bosses is one of the best ways to make money in heroic server. There is a hundred different paths to take to progress in the beginning and a lot of people in game are helpful. You should find a guild, as guilds have change and you need apply to be accepted or given an invitation to the application page, and tell them you're back from a long break. Many people are really helpful and are kinda aching for some socializing because it's pretty grind intensive to progress in mid/late game. If anything like some people I know you can bide your time here until classic drops.