What servants should I save for this 2019?

Eresh,Gilgamesh,King Hassan, choose any of the SSR riders they are all good

From now on until summer, you could get 2 decent welfare servants Archer Nobunaga and Rider Kintoki. Thus I suggest you to aim for Lancer and Assassin first. The day after tomorrow there’ll have a banner features King Hassan who is debatable as the best Assassin. For a lancer, Kana is really good and has a rate up in Valentines banner. For more options you can look up at Fgo JP event list.

Saber:musashi(she is the top tier buster boss killer. also she's 1st skill cover her only flaw. gaining np.
Assasin:hassan(strongest assasin ever. no doubt.
Lancer:ereshkigal(she is also one of the best lancers and she has a great team synergy)
Berserker:mysterious heroine x alter(she is waifu one and i think she fit with jalter because jalter's 2nd skill will provide her +40% attack since she is dragon servant
Rider: I dont know which rider will come but you need to change your riders. astolfo and marie are waifu ones but they are weak