Hello, I've decided to make a lightweight arch based distro as an IT college project, I've little distro experience what things should be done to make a lightweight distro for low end hardware.
Things I'm gonna do are installing arch, iceWM, systemd free and making a customizing kernel for better cpu, ram management.
What things further i should do?

Welcome to LQ.

• Research on the web some ways to build your own distribution, to see what other options exist.
• Write down a list citing the minimum functional requirements for your distribution.
• Determine how you can distribute it so that others may install it.
• Determine how you can archive and manage changes to your kernel, drivers, and RFS content + source. Such as a GitHub repo.
• Please post your results here so that others may try it out and/or critique, plus provide any feedback or assistance. Or also post any points where you're stuck, along with some descriptions of what you have questions about.

This seems to be a continuation of your two previous threads, except you've switched from LFS to Arch.

What prompted you to make this change?

How familiar with Arch are you?

Arch is systemd. If you want that then you may want to start with Slackware. A lot of the software in the arch repos won't work without systemd. You are going to have to start from scratch almost.

Arch is already light. Arch is advertised as A simple, lightweight distribution. A basic install is around 1 GB as I recall. icewm is in the repo.

Compile a Linux kernel, 5.10 has a long LTS date.
Busybox for userland.
Add wifi (wpa_supplicant) and framebuffer vnc
... and vnc into a server box running whatever programs/apps you desire to install/run.
Mine weighs 7.5MB, boots in a second (to around 30MB ram usage) and vnc is reasonable enough to play youtubes in chrome etc.
Adding sound and superior tigervnc and even old/light hardware can yield good/great performance.
Tweak/rebuild the kernel/busybox .config's to your hearts content.

I boot OpenBSD in a similar manner, just base ... plus pkg_add tigervnc and its away. sndiod for sound forwarding from the server to local speakers/headphones. Fatdog (Linux) for the server (headless old tower desktop PC, but long overdue to be replaced by something like a pi, especially given recent rising energy prices).

Lfs miss out alot of things like a package manager and it's not a good base for my project.
I have some experience in arch.

If not having systemd is important to you, you should consider starting from a non-systemd distro.

Only a few of Arch's many derivatives have gone down that path: https://distrowatch.com/search.php?basedon=Arch&defaultinit=Not systemd

Remove the Arch requirement and there are almost a hundred non-systemd distros - you should evaluate whether some of those are more suitable bases.