UKIP need to make more extensive use of Social Media, and resist these attempts to “Monopolize the Internet” by the mainstream.
If there is going to be any money spent - then why not spent it on social functions where one can have a decent night out among people of like mind?
…Surely a better thing to spend money on than ■■■■■■■ into a headwind - chasing votes in wards full of lefties…
UKIP’s best chance - is to go for the disillusioned Libdem Voter (Who represents “Libdem Leave Voters■■?”) and the “Regret voting Tory” voter. Most of all though - get that nearly third of people who can’t be arsed to vote off their arses - and into the polling stations - just to turf out the incument - of whatever party they happen to represent, since it is clearly 100% the case that the incumbent at this time “won’t be UKIP”.
If UKIP have come second to Labour in a seat previously, then UKIP need more voters to switch their habits in the way I’ve described above. I don’t figure there to be much chance of “Eating into the winning Labour candidate’s vote” otherwise.
In wards where UKIP came second to Conservative or even Libdem in 2015/2017 - I would recommend that Labour voters should consider switching to UKIP - just to get the Tory out, where the Labour candidate was unable to make a serious dent in the winning Tory’s poll last time. 
The PR over FptP voting system - can be made to work in UKIP’s favour IF they can “Blanket Field” their candidates, rather than concentrate on just a few “winnable” seats, which is easy for the mainstream to counter-move against. Grimsby? Thurrock? South Thanet? EASY to bat away UKIPs efforts. 500 seats at once all around the country though? - The Mainstream campaingers don’t have enough resolve of their own to stop a multi-pronged approach to taking any and all seats away from them. I would say every seat where there is a Remainer in a Brexit-voting ward - should be up for grabs for starters… 4 figure majorities some of these characters have got even now. It must be easier to take a four figure majority away from a Remainer in a Brexit seat than “concentrate all firepower on a marginal seat where UKIP were not even second last time”… Voters for the incumbent are also more likely to be complacent in wards where their elected incumbent is sitting on a “comfortable majority” as well… This is why elections are never held in August of course… 