Santera provides 20% battery, crit star drop rate and NP strength to Ally. She is a good star bomb as well as a good ST Archer (but I believe Kuro is better) I use Santera to buff then let her die.
Parvati will be your farming Lancer. With 1 Skadi she can go a long way. Parvati loops her NP rather easily while also providing NP gain to allies. Also very self sufficient if you feel your servants lack survival skills.
Diarmuid (Saber) is a lot better than he gets credit for but is hard to complete against servants like Yagyu,& Lancelot. Since your only leveled up Saber is Musashi I would recommend leveling him up when you can afford to do so.
You can skip leveling up Ana right now. Liz has a charisma skill(attack up) that buffs females 2x so it’s worth mention that. Her Defense down is okay too but it’s only 1 enemy.
Suzuka is a buster crit AoE saber but she needs NP levels to preform well. If you like valley girls with fox ears, look no further.
Deon is a solid tank. He can taunt for 3T’s as well as inflict charm. Taunt is very useful in all parts of the game IMO.
Atalanta can generate a lot of stars from her NP but her face cards lack the damage necessary for building her NP gauge. However she can loop her NP with the help of Skadi. She has a Quick card damage up that applies to the party but is only for 1Turn. Her second skill is a crit star gather skill(if you NP back to back you won’t need to worry about leveling this right away if at all. Her third skill is an Evade and NP gain up for 3T’s (this is what helps her loop)
Nezha is okay. At low Np levels her NP won’t hit very hard and since you have Parvati I feel you can skip investing into her for the time being. She also has meh NP gain and star generation.
Marie Caster is a support Caster who provides crit stars and attack up to males. Her other skills are a heal and invincibility making her a little tankier however her low damage is somewhat offputting. Not to mention that she will require shells which are annoying to farm and typically aren’t available from events until Summer.
Nitocris is your new MVP for farming right next to Arash. Nitocris has a instant kill np but it’s “chance” based. Her first skill increases that chance (but don’t expect to go further than silver enemies) she can also charge her Np instantly so people typically give her Scope which you lack , and Black Grail to help her damage if any enemies don’t die from her NP’s effects.
Arash, the best 1* in the game. His job is to nuke , regardless of the enemy class advantage. Give him Imaginary Element, Aerial drive or scope and he’ll will be in a good place. Just work on his 3rd skill. The other two can be completely ignored.
Snek’s can charm lock male servants and trivialize a lot of servant battles. If you are having trouble with servant battles, it’s recommended you level them both up.
If you require supports just borrow a friends Waver, Skadi or Merlin. Merlin will have less value for your roster.