Firearms and stealth complement each other well, in game terms. From the firearms side, you want high Agility and Intuition. The former to fire your weapons accurately, and the latter to boost your initiative and help you make perception tests. And Agility and Intuition are the Attributes that are used for the stealth skills.
I would recommend the stealth skill group, but for firearms, the skill group is only good if you actually plan on using such a wide variety of firearms. Generally, you are better off getting pistols and one heavier weapon type such as long arms or automatics. Specializations might be cheaper after character creation (since 2 build points is generally worth more than 2 karma, the cost to buy a specialization), but it is still worth it for your core abilities, to have those 2 extra dice right out of the gate.
Your main three areas for a ranged combat specialist are extra initiative passes (at least three is ideal, since that puts you past most of the normal security that you will encounter), Agility boosting (muscle toner is the best), and a smartlink (cybereyes are the best, but you can get the same thing from glasses, or even contacts). For stealth, you want a chameleon suit and some tools. If you don't have the build points left for the technical side of covert entry, the maglock passkey and lockpick gun are both useful tools.