help me set up policy-map to aliviate congestion

Hello experts!

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I have a 3850x as my core for all the routing to my sites(all sites are using 3750s), any traffic that's coming from the internet side is coming on a 10gb interface and going out to my sites at 1gb interface. This has caused bottle neck and i am seeing tons of drops on my 1gb interfaces(on my core facing the sites ). Many of you have suggested I either upgrade my links or upgrade my 3850x, at the moment something like this is out of my reach as I don't make these kind of decisions (tho I wish I did..). right now I have no qos or policy map set up. After long hours of research and planning I came up with this plan to set up qos on my interface that's having the most drops, I was following this cisco document when planning out my service policy https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3850-series-switches/200594-Catalyst-3850-Troubleshooting-Output-dr.html

please tell me if I doing this wrong because this is the first time I work with qos and policy maps. This is the action plan I came up with. Please let me know if my configuration will do the job and if I'm applying this policy map in the right place.

1.     create a policy map and apply it under the interfaces with the highest drops
a.      policy-map Buffer_Policy

        class ControlTraffic

        priority level 1 percent 10

        class class-default

        bandwidth percent 90

        queue-buffers ratio 50     

apply the policy at the 1gb interface facing the sites
b.     interface Gi1/0/4
        service-policy output Buffer_Policy

1.     Increase the softmax multiplier
   a.     "qos queue-softmax-multiplier 1200" command

If you guys have any experience is setting up QoS for a situation similar to mine and have a better idea please let me know!! Thanks in advance!