Arabic grammar (see Arabic Grammar) has enough interlocking pieces that the order you learn them in genuinely matters — some sequences make later topics click faster, others create confusion that has to be un-learned.
Nominal sentences (subject + description, no verb needed) are the simplest sentence type in Arabic and let you start forming real, correct sentences almost immediately — "the book [is] new" needs no verb conjugation at all. Starting here builds confidence before verbal sentences add conjugation complexity.
Before tackling detailed gender-agreement rules, learn the single most useful shortcut: a noun ending in taa marbuta (ة) is very likely feminine. This one heuristic resolves a large share of gender questions immediately and gives you a working default while you build up exceptions gradually.
Formal case endings matter for careful, formal MSA reading and writing, but everyday spoken Arabic — even formal spoken registers — drops most of them. If your priority is speaking sooner rather than formal writing, it's reasonable to defer detailed case-ending study and focus on word order and vocabulary first.
Because sun/moon letters only affect how "al-" sounds (not how it's spelled), treat this as pronunciation practice rather than something to worry about while writing — trying to "solve" it as grammar rather than practicing it as pronunciation is a common, avoidable source of confusion.
See also the reference page: Arabic Grammar.
Nominal sentences (subject plus description, with no verb needed in the present tense) — they let you build correct, real sentences almost immediately without tackling verb conjugation.
Nouns ending in taa marbuta (ة) are very likely feminine — this one heuristic resolves a large share of gender questions before you've learned the full set of exceptions.
Not necessarily — everyday spoken Arabic, even formal registers, drops most case endings, so speaking-focused learners can reasonably defer detailed case study in favor of vocabulary and word order.
No — they only affect pronunciation of "al-", not spelling, so they're best practiced as a listening/speaking rule rather than treated as something to solve in writing.