Re: Can some advise me on the best way to farm seals/medallions?
Pick up 3 more and run Foundry t2/Roots of Fangorn t2. You'll probably want a LM/ranged for RoF to make it easier on the group. The Tier2challenges can be completed twice a week with resets on Monday/Thursdays for seals or regular T2 can be run for medallions. Honestly the easiest way to get meds/seals(besides raiding). If you aren't looking at raiding, crafted gear will probably be top tier, but then there is some decent jewelry drops in both Foundry/RoF, then there is the Draigoch set(barter vendor in galtrev) which you can get 4/6 with just medallions(save the seals for orthanc gear if you want that) and also the isengard instance sets which can be bought with medallions/seals from the ox-clan camp.
If you guys aren't keen on doing Foundry/RoF, then 3mans will be easy runs, although they get tedious after a few runs.
I'm personally not fond of skirmish, but you can try those.
Make sure whoever is leader sets up the runs with instance finder to get the +% currency and morale bonuses.
*edit: As a 3man fellow, you guys should easily rip through the Limlight Gorge questline and dailies(in the great river), get kindred with both Stangard and LLG to obtain some very nice jewellry.