Uruwi's Arka portal

Starter resources

The official Arka website is no longer maintained (it seems), but it's a good resource for people who want to learn about Arka.

The Vulgar Arka dictionary is still updated (albeit in Japanese); this is the dictionary you should be using.

Kakis Erl Sax's wiki is a great place for historical Arka materials if you can read Japanese.

Things that aren't mentioned in the official site, at least not well.

o is used before a word starting with a consonant. ont comes before a vowel-initial word.
If you want to relativise an object of a preposition (here, we use "preposition" for what the official site calls "casers"), the preposition should be put at the end of the clause, as done in English while trying to piss prescriptivists off. The city in which we live is translated, for instance, as haim l'ans ra ka (city rel=1pl live in). Omitting the preposition is also acceptable. See this page for more details.
Speaking of which, relativising genitives isn't so straightforward. The above site translates a friend whose father is a teacher as hacn le til kaan lex xaxan (friend rel have father as teacher). What should you do if the clause uses some other verb? Beats me.
You might be confused about "turning conjunctions into casers". In short, a preposition (note: we're not including e, which is special) can modify only a verb by default. Attaching -en allows it to modify a noun instead.

SEREN ARBAZARD SETES SAT XE, HAYU LU ES FOS. el sain sen tu kon fi oktfesk.

The relevant news article was taken down, but here's an archive link (Japanese). I'll leave it at that.