Which 3* servants do you think have a place next to 4-5*

Euryale and Arash can be useful as well.

The 3* servants I have right now are Euryale, Cuchulainn, Ushiwakamaru, Medea, Jing Ke and Hundred Personas. 1-3* servants can be good but their only real weakness is their stats. You won't be seeing any low-tier servant doing well by themselves but with support they are strong.

Since i got golds of every class almost all the low rarities fell into disuse.
Arash is the only one i use regularly because he is just too convenient for farming... He will clear one wave of trash mobs and give his spot to the next party member.
honorable mention to Euryale that can absolutely destroy any male that is saber/berseker even faster than a 5* would.
I would mention Leonidas and George for hard quests when you need a tank but post Babylonia Mashu is crazy strong so I generally use her instead.

More then you think actually.
There are a ton of 1-3* who can be as usefull of 5 star.
Mozard, Usiwakamaru, medea, Arash, cu, robin, ceasar, jaguar warrior, georigius.
Deam, even Gills the rails Saber is quite cool to use !
the only problem they have is thet they need specific team comp to work!
the game compensate it self in this way, stronger servant are less niche, so you can use them almost alweys, but low star have stronger niche then the 5*, so in their specific game they are better.
The perfect exemple of this is Asterios.
He is probabily the most disappointing berserker in the game if not played in specific fight. but in those fight he is absurd.
just go look for solomon boss fight with the dude. he is crazy.
But for 99.5% of the game he is useless.

there are very few servant who are actually useless. like astolfo, arturia lily, boudica, geronimo... phantom of the opera.

I'd level up all servants. You'll never know when you might need someone.

since i only got martha and marie as gold riders i tend do use ushi a lot and medusa(well i use her for waifu reasons xD)
Aside from them i like david a lot and use him with emiya against saber bosses(well he is one of the best hybrid support i know) I like euryale too and i will continue using them at least until fujino chan is out

Don't forget my boy Hans... he's very good, and arguably a more reliable healer than Merlin, with potentially better burst, unless you're a whale

ill go by class

TL;DR my top pick of each class

Caesar, David, Cu Proto, George, Hans, Fuuma, Lu Bu

SABER

caesar: ST NP with good refund and lots of stars. 3 great team support skills that can benefit his own damage as well

bedivere: solid buster ST character if you have him at high NP level

ARCHER
3 star archers are almost all amazing

Robin Hood: spam high power ST NP in artes team.

Euryale: Charmlock males on top of high damage against them

David: amazing support even compared to a lot of higher rarity stuff. can give the whole team hit based evasion on a 6 turn cd and has charisma. youd have to look at something like merlin to really call him outclassed and hes just a 3 star.

Arash: everyone knows arash is great for farming. clears a wave and dies so you can have your team comp ready for the next thing

billy, kid gil, and tawara are all straightforward and effective damage dealers too. only really fall short of higher rarity stuff in raw stats

LANCER

Jaguar Warrior: Solid buster crit character with ST NP

Cu)both of them: both have 3 evades every 5 turns. OG has guts and a heal and Proto has star absorb and crit damage. take your pick.

Leonidis: can taunt tank for a while before his low stats catch up to him and provide stars and a buster buff for the team.

RIDER

George: Best taunter in the game. even with his low stats he has very high defense buffs and a guts so he can easily keep taking all the hit for 3 turns with no support let alone if you provide other buffs.

Ushiwakamaru: strong ST NP with charisma and team np gain and star gen buffs.

Medusa: theres a couple of low star rider farmers, but medusa is the only one with an NP charge skill.

CASTER

Hans: one of the best supports in the game at any rarity. he gives attack up, defense up, crit stars, crit damage, and heals. only lacks hard defense and raw stats to take hits.

Medea: can spam her NP to remove buffs from enemies and has a skill to remove ally debuffs.

Shakespear: good option for farming setups if you lack stuff like waver or merlin. Has a 20% targetable NP charge and a team buster buff on top of his own AOE NP

ASSASIN

not really much outstanding for low rarity assasins, tho theres not many assasins at any rarity. half the 3 stars a competent damage dealers if you dont have a good higher rarity option and Fuuma Kotarou can make a fair bit of stars and give one ally evade for a turn.

BERSERKER

Lu Bu: his ST NP can do more damage than higher rarity counterparts a lot of the time due to NP5 and two damage buffs for it. not much else to be said. decent straightforward buster berserker.

Kiyohime/Spartacus: AOE berserkers for farming. Spartacus has an NP charge skill. Kiyo does more damage with hers.

Not entirely sure about the others but i will always have og lancer cu at the back of my party, he's saved me FAR too many times to leave him out

I still use 3 star servant even i have a buch of sr and 3 ssr notably cu og and proto, ushiwakamaru, leonidas, bedivere and serenity some of the even outdamage the 4&5*