one glance on your gears, you should have no problem doing torment 1 or torment 2.

yes, DPS can be increased by dexterity, critical hit chance and critical hit damage.
at the beginning, you can try to aim for 40% critical hit chance and 300% critical hit damage;
for gems crafting, you can craft till FLAWLESS IMPERIAL / ROYAL gems. FLAWLESS ROYAL is too costly at the beginning.
don't spend too much resources on crafting rare items or enchanting stats because your items will need to be replaced as you progressing.

since auction house is not available in RoS and all legendary items are bound on account, so there is no shortcut to obtain items other than farming hard.
i will suggest focus on legendary set items farming like Marauder/Natalya as their set bonuses is very useful.

you may start with bounty farming, try focus on Act1 bounty as you may have a chance to get RING OF ROYAL GRANDEUR (RORG);
Also, you will get the key to open rift to farm items/Blood Shards (BS);
If lucky, you may get those legendary items from bounty/rift farm.
Next, when you had collected enough BS like 400-500BS, you can gamble with KADALA for specific items like chest armor, glove, shoulder, etc.
You can start aiming for 4 set Marauder bonus (e.g. Helm, Shoulder, Pant + chest/RORG) + 2set or 3set Natalya bonus (Boot & Hand-Crossbow). this combination should have enough for you to bully T1 - T4 monsters easily.
Try look for group farming, it is more efficient because other team members can pass the items to you if they already have it.
Good luck and happy hunting ya ...! 

Dreaming above gave you quite a few pointer already.

But since you are a casual player, better get into a clan and join them for higher Torment rift run.

I cant advice on skill set since i straight away jump to 6 piece Marauder setup.

the worst you can do now, just farm bounties on T1 either solo or join public games.

if you want to get set items fast, provided you have Rift Keys,  join the Rift it Forward community. Farm for Blood Shards (BS) there and spam at Kadala

/casualtip