Hey, I can tell you I was frustrated too at the start of the game.. so few potion drops and powerful enemies made me almost want to quit.
I'm so glad it was this difficult because it made the later stages of the game much more satisfying.
I will tell you the first 10 levels of the game will be a struggle.. you will cherish every single item that drops especially health potions

Also remember that DD is more open-ended than D2. You have to decide what you're capable of undertaking. Nothing is really guiding you in DD as you'll make many decisions.
As Raze says, go as far as you can in the catacombs and then up your XP with orcs. For me, though, the orcs were also very tough so I made a risky move and headed south from Aleroth so I could reach another town called Verdistis (which is on the north east part of the map.. its quite a trip). I recommend you give it a shot though.
Go south and avoid as many orcs as possible.. when you see the bridge , cross it and then start moving north through the farmlands. Avoid the corpses along the way as almost any enemy here is very strong. If you reach a place called the Cursed Abbey (you will know when) avoid it and go around it heading north east. Keep going north east through the forest.. you'll have many enemies following you at this point but don't stop. You won't have a clue where you are but eventually you'll end up on a stone road on the northern part of the map and if you follow it you will go to Verdistis.
This was the best part of the early game as Verdistis has many non-fighting quests available that will help you raise maybe a level but more importantly, you can make some good money here.
Go to the Inn and scout for quests.. also find a character named Sir Patrick to the west in his big mansion.
He can loan you money which you can use to buy some better weapons, armor and potions. (Just don't forget to pay him back!!!)
Scout around and explore and see what else you can find.
When you've been able to catch your breath go back to Aleroth and finish of the catacombs.
This worked like a charm for me. I'm now level 23 and I just cleared out the entire orc camp to the south east. It took me 3 hours but it was worth it! Don't underestimate the enemies you meet, though, as some will really test your skills.
The game is a blast after you get some good weapon and armor drops so don't shy away from scouting every little corner of a dungeon or certain area. You can miss out on something that is really valuable.
I've played Diablo 2 for quite a while but DD does it for me.. its got the Baldur's Gate quests + the action from D2.. its the perfect combination.