Who to save for in 2019?

Melt and Summer Nero I would say. Nero is a great farming servant and had outstanding skills. Nero is prob the best unit we going to get this year imo. Melt is nice ST quick unit but has some downsides with her skills. They get fixed later on so its fine, I would save for those two units.

If you already have a good assassin, you could pretty much skip old man hassan. He is a good solo servant but I don't solo stuff so he isn't worth picking up. I would say Abby would be nice to have, but right after her rate up we get a better unit than her. Since you F2P should come down to who you like the most. Gameplay wise Nero is the best bet this year.

King hassan is an absolute unit. he has a rateup later, so he isnt necesary atm, but he is still amazing. his NP gain is amazing despite his buster deck. his skills are amazing as well. he has a five turn guts, thats better than Cu. it also brings him to 5000 health at max level. his skill Protection of the Faith A+++ gives him all the buffs he could ever want. his Evening Bell EX skill gives the entire enemy wave death resist down for three turns. with his instant death np, his great NP gain, and a great support you might be able to NP two turns in a row, almost guaranteed to instant kill (unless its a servant and he can pull off even that) even without that buster NP damage. oh and Evening Bell has a buster buff.

Abby or Hokusai? Im going with Hokusai myself. I count Hokusai in this as she is right around new years, so she might as well be on the list. Abby, while her buff remove NP can be very usefull, she isnt going to be putting it out very often. other than that, her partywide NP battery is her only good skill.

Hokusai however is a great arts servant. her star gen is decent, aided by her Existence outside the boundary passive. her first skill is a 1-turn Evade, as well as an NP battery (30%). this gives her good survivability, able to tank enemy NP's, as well as improving her NP gain. her NP gain is decent, having two arts cards. she can NPAA chain, allowing for good NP refund. she is easily spammable. her second skill gives her a 3 turn Arts buff, which increases her NP gain, and her damage. now, one pro of Abby is that her np has very few hard counters. two that I can think of. Hokusai is one of them due to her second skill, which in addition to an arts buff grants a debuff resistance up, and a debuff removal resistance up. if Abby cant remove her buffs, that means no damage to Hokusai due to her evade. her third skill is an arts based damage buff, but in another way. for three turns, every time she hits an enemy with an arts card it inflicts a defense down (10% at lvl 1, 20% at lvl 10). this lasts for three turns. if she hits two times with an arts, each inflicting a maximum of 20% defense down, thats 40% for one turn. repeat that for three turns and you have a total of 120% defense down. while it locks you into attacking one enemy or sacrificing straight damage for more targets, its a better damage buff than many support servants. her only real downside is her AoE NP, which is an arts NP dealing extra damage to enemies with the man attribute. other than her NP, her kit is perfect.

I dont really need to explain BB or other free servants, they should be acquired if possible.

other mentions:
Proto Arthur, I will likely be rolling for him
MHX alter, I havent analyzed her kit yet but I know people will be rolling.
Melt and lip? they only show once so you better decide so you dont regret. their alterego class is a definite plus.
Holmes?
Edit:
old man Yagyu is a great pick as well, rolling for him is a must if you dont have a good arts saber

-King Hassan
-Musashi
-Abigail Williams
-BB
-Meltlilith
-Sherlock Holmes
-Summer Nero
-Ereshkigal
-MHX Alter
-Yagyu

Not necessarily in that order but those servants are considered the top 10 of 2019.

Save 4 Alterego and Foreigner class rate ups.

They're limited and super useful.

If you have arts crit servants as Chloe, Nursery and Saberlot, Holmes is a must as well.

Aside from that, I will be saving 4 waifu (Okita, Summer Nito, Tomoe Gozen and Abby) for the entire year...

- For offensive caster, go Summer Nero.
- Melt is good, yes, roll for her, and hope you get passionlip too, she's also good.
- From what I can see, you lack a good ST saber. Musashi comes back for Shimosa and Okita comes back for GudaGuda. Both are good.
- MHX alter becomes one of the best berserkers when paired with Skadi. Bit of a long-term investment.