It's really unfortunate but you won't easily find people to do T4 raids. I believe T3 raids right now are irrelevant, only noteworthy is Jynx cause she holds the best Ice dps right now (surpassed by Mewtwo but that's a legendary and needs rare candies). It's a soloable raid but even if you can't there's a chance you will convince someone else to help you. There's also Alakazam who is harder than Jynx but is also obviously outclassed by Mewtwo as a Psychic attacker
T4 raids on the other hand will need 3 people at least since you just returned and you don't have the supreme counters to 2-man them. The most important T4 raid is Tyranitar. Absol and Houndoum probably have some use but are far less important. Your best bet is to propose a Tyranitar raid a day that there are only a few people from your group available and you might not be able to defeat a Mewtwo. Generally everyone is doing Mewtwo raids and he has been a T5 raid for two weeks. Perhaps late October people will be bored of Mewtwo raids and you'll find more people to do T4
Raid boss list now is Psychic-heavy with the exception of T4 Dark types. Gengar has the best dps against psychic types but he is fragile and dies very quickly if the boss has Confusion. Tyranitar is excellent. If they are available in your area, Houndooms are a budget choice until you get the former two.
Meanwhile you should have some fighting types to beat the dark bosses, Machamp is the fighting king, Hariyama is a bulky alternative.
Ultimate goal should be level 30+ Mewtwos, Tyranitars and Machamps. If you find someone willing to trade with you legacy SC Gengar or SB Mewtwo add them to the ultimate team.
Hope this helps!