ok, terms:
vdev = either a single drive, or a single raid array
pool = a group of vdevs over which data is split up (somewhere between JBOD and RAID0 of all vdevs in the pool)
use the 500GB samsung F3 as a boot drive to install the OS (by itself).
Then do one of the following 3 options:
1. Create multiple pools of 1 vdev each, each vdev being RAID1 of 2 identical drives.
This is great for upgrading, downgrading, etc... pools cannot be shrunk or have vdevs removed, you can only replace vdevs in a pool (or backup your data, destroy it, and create new pools). This is a problem for upgrades and the like which you can solve via multiple pools. You can, however, add new vdevs to a pool.
What do do with drives drives:
2x 1TB Samsung F3 - use as is
1x 2TB Samsung F4 - buy a second one, or sell it.
1x 1.5TB WD Green - buy a second one, or sell it.
2. Create a single pool of multiple vdevs, each vdev being RAID1 of 2 identical drives.
This is less flexible, but gives you better speed and is more convenient in terms of file sharing (only one virtual drive).
What do do with drives drives:
2x 1TB Samsung F3 - use as is
1x 2TB Samsung F4 - buy a second one, or sell it.
1x 1.5TB WD Green - buy a second one, or sell it.
3. Get more drives, make RAIDz2 array (aka RAID6 array)... for ideal performance 6 drives should be used (I am using 5, but turns out that performance is better with 6+, however, reliability suffers... its best to not go higher... so 6 for a RAID6 is ideal).
3a. use 6x2TB drives for the raidz2. (giving you 4x2TB space and double redundancy)
2x 1TB Samsung F3 - sell them
1x 2TB Samsung F4 - buy 5 more
1x 1.5TB WD Green - sell it
3b. use 6x1.5TB drives for raidz2. (giving you 4x1.5TB space and double redundancy)
2x 1TB Samsung F3 - sell them
1x 2TB Samsung F4 - sell it
1x 1.5TB WD Green - buy 5 more
3c. use 6x1TB drives for raidz2. (giving you 4x1TB space and double redundancy)
2x 1TB Samsung F3 - buy 4 more
1x 2TB Samsung F4 - sell it
1x 1.5TB WD Green - sell it
Summery:
Plan 1: Easiest to upgrade/downgrade/sidegrade/whatever, less space, less redundancy. Might be cheaper if you chose to have fewer than 6 drives.
Plan 2: Harder to upgrade (equal to plan 3), less space, less redundancy (worse than p1). Might be cheaper if you chose to have fewer than 6 drives.
Plan 3: Harder to upgrade (equal to plan 2), more space, more redundancy. Requires 6 drives.
Speeds: plan 2 will be faster than plan 1. But its hard to say whether plan 3 or 1 will be faster.