It's not explained at all ill give you that, but its actually quite easy to pickup. This wont be a perfect guide but it willl hopefully help you get used to the game .
When game starts, the NPC will be getting out of Heli to give you the drill, the second you place the drill on the hive you will notice at bottom left of your screen a challenge box appears. The challenges for the first hive are like 1 of maybe 3 random challenges, Use only melee to kill, take no damage and maybe 1 other. Completing these challenges will give you one skill point to allocate for the TAB menu (perks). I highly recommended to do all these challenges as for completing one hive you get 1 skill , point, so if you do a challenge and destroy hive, you get 2 (essentially making you twice as strong for next hive).
You have 4 support options on your first loadout. these are activated using the keys 3-6. each have different prices, you can tell by the UI on bottom right of your screen. Pressing 3 will place a sentry gun (manual firing), 4 will place a IMS system, 5 will drop an ammo box and 6 will place an explosives box(gives semtex). As you level up you gain other options to change these out.
At the start of the game, if you're playing with more than one person, id recommend talking to other players to plan a strategy (basically what you're all going to do). first make sure they all know to aim to complete challenges. no aliens will spawn until you plant the drill, so take advantage of this time to plan. Im not 100 percent sure yet, but i believe its the same everytime you move onto a new hive, there will be a break period where you can have time to plan your strategy before you plant drill. I recommend not buying another weapon yet, wait until maybe third or 4th hive because you may get a challenge that says kill aliens using smg or assault rifle, so you dont wanna be wasting money buying a weapon and then having to change it out again for another challenge. Weapons are found like you said after first hive, the one i find easiest to spot is just behind the first hive, if you hug the left side of the map, its about 30-40 feet past that hive lying up against a fence.
After destroying 4 hives, you will come to a barrier hive, this cant be destroyed with the drill, so a heli will come in to start destroying it, so your only task it to kill aliens. After it is destroyed, there will be a money box in the floor of the hive. The most money you can have is 6,000.
Since you must be low level, id suggest spending all your perk points on the pistols skill tree. i think the first 3 upgrades cost 1 point, the next 2 points and the last 3 points. when its at skill level 4, you can now carry to primary weapons with your handgun, very helpful . If you're playing with other players it s a good idea to have your other points spent on 1 other tree, while having your team-mates spend it on a different tree. This way you will have someone who can throw down a max ammo box, have another guy that has the most powerful sentry gun, another max IMS system and someone else with another beneficial package (if they above level one, they maybe able to throw down max armour).
Ill have to make a good video to clear it up more but i hope this helps, for now just make sure to make use to time between hives to get used to where everything is on the map (finding weapons, traps etc). Hope this helps even a little .
Thanks! That helps a lot!
I already figured some stuff out, and would like to add to your answer:
money box after a barrier Hive has $3000, so its a good idea to buy some ammo/armor so money isn't wasted.
You can buy more than one ammo box and more than one armor, if its level is not max, they'll add up (so you can fill up armor with several purchases).
Its a really good idea not to spend money on a gun right after the first or second Hive, as they often give you a "pistols only" challenge.
As for pistols skill tree - I didn't even notice it allowed you to have two primary weapons! Thanks!
As for barrier Hive - if you shoot it, it will get damaged. If 4 players attack it at the same time, it will go down much faster. To make it easier to survive in this period its a good idea to activate all nearby traps.