First checkout Alpha's incredible guide on the extremely early and Early-game Extremely Early-game Early-game

Explore! In this Modpack exploring is a must, try to find Towers with Waystone and a loot chest which can contain useful items from other mods that can help you start them much early and/or easily. Loot waystones from the towers, they can help reach great distances like when you use /rtp command and found some useful places that you would loot but didn't had space. Place Waystones in your base and later in the Nether and The End to tp in the dimensions without going through trouble of going into the portals.

I've found that easy, but not much of exploring method of travel is by using grappling hook under the islands between them and the void, just by grappling in the bottom of the islands proves one of the useful methods of travelling to great distance in my playthrough.

In the Early game I would recommend using Sophisticated Storage as your first storage, it provides barrels with size and stack upgrades equal and bigger than double chest, which should be helpful when you return home from exploring. After you've collected enough resources start Refined Storage, build a controller, crafting grid and a disk drive with storage disk for your first network. If you want more information on the RS checkout official wiki Refined Storage.

You can get early RF for Refined Storage Network with Powah mod Thermo Generators Which easy to craft, provides good early constant power generation, they require heat source like lava underneath it and constant supply of water. You can get water supply from the infinite water sources and manually feed them water, or with placed above the water sources Drain from EnderIO which require Capacitor to work and store energy, you can supply water from drain to generator by using fluid conduit from EnderIO. You can use cables from Powah mod to power your network, just place cables from thermo generators to your Controller from RS. Congratulations on your first Storage Network!

Use backpack and it's upgrades, try to upgrade backpack to different tier as soon as you can. Useful upgrades are stack and craft upgrades. If you don't have Hero's Medallion from Reliquary mod which can store exp, then craft exp pump and tank upgrades to store exp.

Upgrade your grappling hook! My preference is to use Ender Staff with Swing upgrades, cause with this you unlock a very unique gameplay later on.

Try to get your hands on elytra as soon as you can, you can place them in the bubbles slot. To replace rockets you can have a grappling with ender staff upgrade to help you gain momentum and height, you can refresh it by simply throwing hook and retrieve him right after he landed on the ground and use ender staff again.

Enter Twilight Forest as soon as you craft iron gear and better shield, try to find something like earth pimple, in them along with monsters and spawners it has great quantity of ores(coal, iron gold primarily, sometimes regular vein of diamond if it's a big pimple).

In The End try to find something like round black chunks like fallen meteorite, they contain Uraninite ore from Powah mod, they used in the Powah reactors, try to get as much as you can, it will help power your reactors for time being before you start your autofarm them with Laser Drills From Industrial Foregoing.