help starting 3.5 m/o on routine?

ℬrandy💫

How the heck do I start my 3.5 month old on a routine/schedule and should it be baby led, parent led or combo?

I'm totally clueless, FTM here guys. My LO is 15 weeks old and thus far I have been doing everything her way, whenever she wants something I give it to her pronto and haven't put too much thought into a routine everything is just nonconsecutive, it's not at all a bad thing but I've read multiple times that babies (not to mention I do as well) like routine. I'm desperately wanting to give it a go. I've done a ton of googling and found different samples but I'm not sure how to implement the schedule; I do not want it to be strict because of course it will vary each day but you catch my drift. I'm stumped however because my LO's current schedule is ALL OVER THE PLACE! Sleep and eating patterns out of wack, etc. 😖

Here's her "routine" 12/27 - 12-29 (I sometimes forgot to jot things down.) 

*12/29*

🍼4oz @8:35pm

🛁@9:45pm

💧@9:50pm

🍼2oz OC @11:15pm

💧💩@12:15am

🍼2oz @1:00am

💤@1:00am

🍼2.5oz @2:15am

*12/28*

💤 @2:07am

🍼4oz @6:25am

💤@6:30am

🍼2oz @9:00am

💧@3:45pm

🍼4oz @2:00pm

💩@3:30pm

🍼3oz @ 3:45pm

*12/27*

🍼3oz OC @ 3:15am

💤@3:20am

🍼3oz @3:30am

💤@3:45am

💧@7:20am

🍼4 oz @7:35am

💤@8:00am

💧@10:45am

🍼3oz @11:00am

🍼banana baby food @11:45am

💩@12:00am

🍼1.5oz @12:50am

🍼5oz @3:00-3:35am

🛁 @9:30pm

💤 @9:40pm

🍼 4oz OC @10:35pm

💤 @10:40pm

Tips & advice would be IMMENSELY appreciated! Also, if you could clue me in on your LO's schedule to give me an idea of where to start that'd be perfect.

TIA ladies💞