So you want a keyboard/mouse and headset for $70? You're not going to get much in the way of quality.
Basic headset/mic that people seem to like and has gotten decent reviews would be a Logitech G230. Runs about $37.
For keyboard, you're not going to be able to go mechanical without hitting the $70-90 range.
A good low cost mechanical, with lighting is the Logitech G710. Runs about $70 in the right places. Uses Cherry Blue switches. There is a Plus model, runs a lot more but uses Cherry Browns.
For a good membrane keyboard, the SteelSeries Apex 300 is backlit and low profile. About $70.
For a mouse, you wont be able to go super fancy but the Steel Series Sensei [Raw] is supposed to be solid. Runs about $42
These are all parts I set up as options for a friend who's building up a gaming rig as we speak. These are not the cheapest options but are ones that have good user and professional reviews. If you dont care about a keyboard/mouse for gaming, or want to invest more later and just need something for now you can get a basic keyboard/mouse combo with the Logitech MK120 for $15 and throw the rest at a slightly better headset like the Logitech G430 which runs about $55.