I'd give them:

120mm mortars - Easier to manage logistics for than a howitzer battery. Pound those dug in Russian troops!

MOAR Drones - They are already using them to good effect. Again, jet aircraft need a shitload of logistics and when they go down, they take the pilot with them, unless recovered successfully. 1-2 million for a Bayraktar beats 24.8 million for a Mig-29.

MOAR things that need the /Guided qualification - Javelin, NLAW,
Stingers, etc. I'd like to see some cheap, medium ranged SAMs for them. Buying older Soviet systems like the SA-6 and such would be a good option. Shore based ASMs would be useful here. I think some of the nordic countries have relatively portable coastal defense Hellfire systems that would be very useful.

If this all seems like war on the cheap - it is. As Teg pointed out, Ukraine needs to be purposeful about reconstruction and preserving funds for that should be a priority.

Also - 2-6 training camps either in or outside of Ukraine. Have the Ukranian's rotate out company/battalion level units for training when/where possible. My understanding is that manpower isn't an issue - they are engaged in a national level mobilization of every military aged male. Training should be a priority - their performance to date shows impact of Operation ORBITAL and the like.