Advice on partiotion scheme

Hello, dear misc

I want to use openbsd for daily tasks on my laptop, I'm planning to
build ports by hand and I want to try some development of the system
itself.

At the moment I'm just playing around and I faced a little problem:
space allocated by default partitioning to /usr ran out in a blink of an
eye. Current df:

$ df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/sd0a 1005M 61.1M 893M 6% /
/dev/sd0k 98.8G 3.2G 90.6G 3% /home
/dev/sd0d 3.9G 724M 3.0G 19% /tmp
/dev/sd0f 2.0G 2.0G -91.1M 105% /usr
/dev/sd0g 1005M 177M 778M 19% /usr/X11R6
/dev/sd0h 9.8G 1.0G 8.3G 11% /usr/local
/dev/sd0j 2.0G 850K 1.9G 0% /usr/obj
/dev/sd0i 2.0G 861M 1.0G 45% /usr/src
/dev/sd0e 18.3G 12.0M 17.3G 0% /var

I want to reinstall OpenBSD from a snapshot and pick a custom partition
scheme. Based on the needs described above, what partitions should I
keep and what sizes should I peek? I know about the workaround with the
/usr partition by setting a few variables (WRKOBJDIR, ...) in
/etc/mk.conf, but I'm not sure if it's the best solution. May be just
give more space for /usr/? Also, is so much space for /var really
needed? It empty at the moment, will daily desktop usage/little OpenBSD
development fill it up?

Also, I'm confused with such a small amount of space for /. Is 1G
enough?

Thanks in advance!