The most important kit ..... a positive attitude and a big smile!
All the advise on body armour ....laugh and move on ... if you need body armour you could use a platoon of Marines better. When the shooting starts, you should be miles away.
Meds - Basic first aid kit and make sure Imodium and Valoid's are in there as well as a local anti-bacterial salf ...I like Bactroban but your call. Get a broad spectrum antibiotic as well. Plasters, tweezers always work well. Take a personal IV and injection kit ...if you need medical attention, the hospitals do re-use these and you could end up much worse with AIDS, Hepatitus or such. Make sure you have a valid yellow innoculation card and get all your shot ....3 months before you travel and boosters before you leave if you can ....take the cholera shots ...... yes, do take the cholera shots!! Cholera is around so a few bags of rehydrate works wonders.
Take out a solid medical insurance thab will airlfit you out. DRC has flights to South Africa daily ....... you don't want a local doctor to even look at you. Stabilise and EVAC ...... make sure you are covered! Make sure you have their local contact details in a safe place.
Basic hygiene is very important. Don't drink untreated water and in remote areas, don't even trust bottled water. Some clever souls buy caps and fill with local water ...don't learn the hard way. I carry drops to purify everything .. I am paranoid, I know but I am still alive!!
Malaria area ...... if you are not on meds I would take meds as a precaution,. Yes, if you live there, taking meds has long term bad affects but for 3 weeks ... it is the safest option. Avoid being bitten ....DEET, mosquito nets and long clothes all helps ...... don't mess about with this!
Food ...... if you don't peel it, don't eat it. If you cannot cook it, walk away! Salads are washed in untreated water ..... don't do!! Drinks .....Coke is everywhere and straight from the bottle .... ice is untreated water so stay well clear of ice.
On gifts ...... don't do it!! The next poor white traveller will be chased down for the gifts. Pay a fair price for a fair piece of work or service. Some say bring candy .....yes and how far do you think their dentist is? Don't travel in 3rd world areas with a 1st world mentality. Your 9-5 job, dual income and 2.4 kids have no bearing here.
Africa can be violent but normally concentrated around big cities/towns. Do some homework before departure and avoid those areas. As for local language and customs ...forget it!! DRC has about 30+ dialects so French will work just fine. You are white so you will be cut some slack ... they expect you to be an idiot so if you do do something offending they will most likely laugh and tell you not to do it again. Apologise and learn ..... Africans are some of the most friendly people you will ever encounter.
Keep personal documents on you at all times, Get a waterproof carrier and have certified copies of all passports and CC's at a safe location. If you do loose documents, the US Embassy will be much more helpful if you can give some proof that you are indeed who you claim to be.
Don't take anything you cannot afford to loose. Knives and kit may be lost, stolen or liberated. A good combo if you do jungle trekking is a machete, a 4 inch knife, multitool and a headlamp. Taker spare batteries for your lights. A SAK always works well and doesn't atract a lot of attention. Carrying water on your person is a must in the bush. Add a SS cup and you can also boil food/water. Make sure you also have way of starting a fire and purifying water. One of those hammock that are rolled into a fist size is very hand. You can sleep off the ground if you have to, use it as a gear carrier and even fish with it.
Insect repellant is a must and I prefer 70% DEET (Uncle Ben's) I am sure there are others that works well but do you want to travel all that way and find out it doesn't ;-)
Dress ....... Indiana Jones style and you are asking to be mugged. Tone it down. A solid rain jacket as it will rain ..... it is a tropical forrest. Quick drying shirts and pants will be great. Jungle boots that protects your ankles is always a winner. Don't take new kit .....blisters will pop and become septic. A hat that can be crushed into a ball when not needed, like a Tilley is great to have.
Keep your feet as dry as posisble. Every stop, take off the boots and socks to allow them to dry out. Take a small container of foot powder and treat each night and morning. The last thing you need is a fungal infection. Look after your feet, they are your transport.
You need at least 2 packs ...... one to leave at the start for the kit you need to fly in and out ...most upmarket hotels will have a safe keeping facility. Leave copies of all documents in this bag as well as a spare CC or such ..... A pack allows you to push through crowds but beware of items hanging out or visible ... you will loose them in a crowd. Add a few garbage bags (5) ....wet kit can be packed into them to return without destroying all the clean stuff. A bag or two will not be a bad idea on your jungle trek ...collect water and emergency shelter
Keep at least a $100 in 1's and 5's on your person. The dollar is still king but Euro catching up fast. Buy a small cheap wallet and carry about $20 in there. Your main stash should be hidden on your person and in case of a mugging .... hand over the worthless item.
Never let your passport be taken out of your sight! Never! Be polite but be firm.
Check in with your local embassy on arrival and tell them about your plans. Leave a written brief with them as well as emergency contact numbers. Ask about areas you plan to visit ..... good info and can be trusted normally. Beter to start searching after 4 weeks than bones found a year later. Report back when you return.
Take as many photo's as you can ..... keep your kit dry.
Navigation - Even if guided ...try and get a map of the aree, even a small compass is better than nothing and a GPS. Update position daily.
Help - Missions are still your best bet. Good medical care, often EU trained doctors and a wealth of local knowledge. In fact ....don't move past one in the bush without stopping. You will always be welcomed, share the news ...word of mouth is often the only comms they have and get an update on the area you plan to travel .....don't give details .... you could be walking into an ambush!
Locals - They can be bothersome and insist on helping you. Be polite and friendly but always firm. They will get the message in the end. You look like a wandering ATM but do not give money away for nothing. Get them to clean your kit ..... (Eish, be careful they don't steal it), wash your clothes or something. I found women more trustworthy than the men ..... avoid drunken idiots!! Run like hell if you have to but don't get physical if you can avoid it. African jails are no joke!
You will be amazed at Africa .....bush one second and then ... a GSM tower. Get a local prepaid SIM card and a cheap cell. Make sure your contacts have this number. In Africa, you don't pay for incoming calls and although coverage will be patchy, any reasonable sized town will have coverage ....... service may be crap though.
Make sure you have a Gmail or such account ..... compile a contact list and every time you get to a internet access point, update on location and travel plans. You are sharing the experience and your backup knows where to start looking .... Africa is big so any little bit helps.
This just off the top of my head .... hope it helped.