How to not use up 3G on iphones?

3G or LTE whatever but i use my twitter app and my tumblr app a whole bunch, and sometimes my instagram but when i do i usually use up so much 3G and i really don't mean to it's just better on the phone for me and i don't feel like bringing my laptop downstairs or something my phone is just with me and yeah. I was just wondering on how i can't use my 3G or LTE as much? I'll be connected to the internet but it'll still rack up? And i've been putting it on airplane mode and then connecting to Wi-Fi. Will this use ANY of my 3G/LTE? I have iphone 5 btw but i don't know if its called 3G or LTE because LTE is on the side… Thank you so much:-)

It it says you are connected to Wi-Fi, you are not using cellular data.