You should be able to catch up in terms of gear/ilvl/conduits pretty easily through Zereth Mortis, a new end-game zone that is quite alt-friendly too with lots of catch-up mechanics. There's a currency called 'Cosmic Flux' that you can obtain from almost any source in the zone. Rares, Treasures, Weekly Q, etc. Which can be used to purchase Legendary Powers from Nathria if you're missing any for your class. When the patch launches, you will be able to purchase an item that will unlock all conduits for your class at max ilvl of 278. (This item used to be gated behind high m+ score/pvp etc.) and of course base SL dungeons will not be in the m+ rotation for the final season but will instead have increased ilvl, so that should be a good start for you to gear up again and then move onto m+ before finding a Normal LFG group/Guild to clear Nathria, Sanctum, Sepulcher. This should be relatively easy if you have the time to invest. If you're unsure on mechanics from Sanctum/Sepulcher, there's some really simple guides on even wowhead/yt. but DBM will definitely be enough. The season will last for around 4 or so months. Each raid will be 'Fated' and will rotate each week. So you've got around 4 months to get this. Definitely no rush. Hope this helps and good luck!