There is some few things what you need to control, to get good acc at streams.
-Timming starting the pattern.
Use music, hitsounds rhythm, rhythm sense and reading. Playing maps around 3*-4* increasing the OD using game editor and trying to improve your acc, should help you a lot. Also play maps where you get around 99% acc for a while.
-Reading at every stream circle.
This is something what you will not need at all in the future after get muscle memory and learn to use rhythm sense in the game, but it's something you will need to work on the most for a while. Is as simple as just click each circle 1 by 1, instead rush or try to predict.
You can practice this at low bpm streams adding Halftime mod. You can also add Hidden or Hardrock with the Halftime mod if you fond it more helpfull to increasse the acc, or don't. Just test it. Use maps like this to practice:
https://osu.ppy.sh/b/1042025&m=0 Insane diff + Halftime mod. Go for really good acc at each stream circle alternating.
-Finger control and coordination. You get it just by improving timming, reading and by practice easier stuff you can stream on. You improve it by playing heavy burst, and long stream compilations.
https://osu.ppy.sh/s/40405 Play this a couple times without retry, using Halftime+Nofail mod, focusing on reading and on keep the fingers movment stable (seriously focus a lot on fingers movment to make sure you don't fingerlock, or you don't increase/decrease the fingers speed for no reason.
Play 2* maps alternating, may be usefull to you, in order to be warmed up to face 3*-4* streams.
-Be able to find, understand and play the bpm.
This is a mix of everything and need tons of hours, you can find your own way to find the bpm. Need time. You will need to build specific things to play each map. Some need more stamina, others more speed, others better reading... Play tons and tons of different maps.
As general advices, focus on stream maps you get the better acc at, and improve on them first.
Play a lot of maps what are not a stream spam, but have a few of them. Improve acc on them. Like this
https://osu.ppy.sh/b/823688Your stream skills will improve even without practice them, so if you feel mindblocked or stucked improving at them, just play normal maps. Also after some practices you may need from several days to a week or 2 to recover, so try to don't force yourself or you will need tons of time without touch the keyboard to full recover and start to be able to approach a good practice.
Don't play bpms out of your confort zone unless you can use only reading to play, so you don't get bad habits.
I'll give you some of my favourite stream maps what may be usefull to have:
https://osu.ppy.sh/b/715345 Memme - Starving Days
https://osu.ppy.sh/b/830322 Goreshit - burn this moment into the retina of my eye.
https://osu.ppy.sh/b/718156 DragonForce - Defenders
https://osu.ppy.sh/b/847313 Feint - Tower Of Heaven (You Are Slaves)
https://osu.ppy.sh/b/550235 Our Stolen Theory - United (L.A.O.S Remix)
https://osu.ppy.sh/b/1001682 DragonForce - Through the Fire and Flames
https://osu.ppy.sh/b/1033154 9mm Parabellum Bullet - Inferno
https://osu.ppy.sh/b/299011 Childhood Crusher-P - Calalini
https://osu.ppy.sh/b/1256809 Avenged Sevenfold - Save Me
https://osu.ppy.sh/b/663881 Yuyoyuppe - AiAe
https://osu.ppy.sh/b/817623 Camellia - d:for the DELTA
https://osu.ppy.sh/b/796161 Epica - Martyr of the Free Word
https://osu.ppy.sh/b/403050 Mitsunori Ikeda ft. Aimee B - Fallen Angel (El Poco Maro Remix)
https://osu.ppy.sh/b/718679 Positive MAD-crew - Mynarco Addiction
https://osu.ppy.sh/b/1192807 Ke-ji feat. Nanahira - Ange du Blanc Pur
https://osu.ppy.sh/b/315010 Sakuzyo - Scattered Rose
https://osu.ppy.sh/b/126645 Xi - FREEDOM DiVE
https://osu.ppy.sh/b/1413768 Xesi x Masew x Nhatnguyen - Tuy Am
https://osu.ppy.sh/b/1345663 Feryquitous - Strahv
https://osu.ppy.sh/b/1216297 Deathstream Training #2 - Marathon Stream Training
https://osu.ppy.sh/b/803828 Apocalyptica - Reign of Fear
https://osu.ppy.sh/b/264791 Various Artists - osu! ~ Death Stream Compilation 2
https://osu.ppy.sh/b/729619 Arctic Monkeys - Balaclava
https://osu.ppy.sh/b/543221 DJ Amane - Drop It Down Like (fang Remix)
https://osu.ppy.sh/b/951778 Days N' Daze - Misanthropic Drunken Loner
https://osu.ppy.sh/b/1251955 M2U - Wicked Fate
https://osu.ppy.sh/b/281843 Demetori - Crimson Belvedere ~ Eastern Dream
https://osu.ppy.sh/b/132466 Megpoid GUMI - Rubik's Cube
https://osu.ppy.sh/b/1129145 Snails & Pegboard Nerds - Deep In The Night
https://osu.ppy.sh/b/710478 Arai Yumi - Contrail El Poco Maro Remix
https://osu.ppy.sh/b/648081 DragonForce - My Spirit Will Go On
https://osu.ppy.sh/b/495651 Ice - L (Lost, Loneliness, & Liberation)