Well, I've never actually tried such a character myself, but there are a few things you'll likely want to consider:

To be good at guns, you need to have a decent perception stat (this helps you hit guys) and a decent firearms skill (makes you better with guns in combat). You will also probably want to have a technological aptitude, as the higher your technological aptitude, the better your guns will work for you. The easiest way to get technological aptitude is to spend points on technological skills, like firearms. You also will likely want to learn some gunsmithing, which will let you build your own guns out of stuff you find lying around. This makes it easier to get better guns as they're often hard to find, and it will let you make your own bullets, which is nice. Keep in mind that to build something, you'll need a schematic, some of which you get just by increasing your gunsmithing skill but others you will have to buy or find. In order to get high levels of gunsmithing, you will need to raise your intelligence; there's an intelligence requirement for each level of gunsmithing.

To be a decent melee fighter, you will want a good dexterity stat, which will give you more action points in a combat turn and will make you more accurate with melee weapons, and you will want a decent melee combat skill. Since you'll be a tech-aligned character, avoid using magical weapons, and instead look for technological weapons. You could even consider learning some smithing so you can make your own technological melee weapons, but there are also NPCs who can smith for you. Also, having higher strength will increase your melee damage (but not your gun damage).

That probably sounds like there's a lot of things you need to spend points on, but it's actually not that bad. I've done a purely melee character and I was able to completely max out my dexterity, melee skill and strength before I was even halfway done with the game, which made the rest a little boring. With two things to focus on, you can be developing your character the whole time.

In the beginning you may find that you are using melee a little more often than guns because the early guns are a bit weak and bullets are limited. But later on you may find you're using guns more often as you find better ones.

Oh, and since you'll be a tech character, use tech healing instead of magical healing. Healing salves will work well for you but potions will not work well at all. NPCs who cast healing spells on you will not be very effective, but NPCs who make healing salves and antidotes and such will.

I hope that helps!