Of course we're light years behind Chelsea - apart from Cahill (who joined about then) their side has been rebuilt in the past 5 years (David Luiz left and returned). Basically they shipped out Torres, Cole, Lampard, Terry (this summer), Essien, Ramires, Branislav, Cech, Malouda, Mata, Mikel, Sturridge, Lukaku (whom they might want back), Bertrand and others who came since and went like Schurlle and Oscar.. They have the power to churn their players over and replace them with new blood - like Hazard, Pedro, Courtois.. their current squad and whoever they've got out on loan.
So we could forensically go through all the Spurs, Chelsea, City, United and perhaps Liverpool and Arsenal squads and compare their depth to ours. For us to be consistently their equal we need to think about shifting nearly all the established first teamers and maybe a few of the youngsters. Right now if you ask me "who, presently on our books, would I WANT to see still in an Everton shirt in August 2019" (start of next season plus two) giving us 5 windows to resolve.. and accounting for age, ability etc. then I say - with good fortune (wanting to stay etc)
Definitely: Tom Davies, Romelu Lukaku
Probably: (barring significant upgrades to side greater than present): Morgan Schneiderlin, Gana Gueye
Possibly: Seamus Coleman and Ross Barkley, Leighton Baines at a push
Young players worth persevering with: Lookman, DCL, Holgate, Walsh and 2 or 3 others who haven't been given a chance yet
The rest: Too old, injury liable or just not good enough..
Robles, Stek, RFM, Williams, Jagielka, McCarthy, Barry, Besic, Deulofeu, Cleverly, McGeady, Henen, Mirallas, Bolasie, Lennon, Niasse, Kone and the rest of the kids (definitely to include Garbutt, McAleny and some others I'm not sure about through lack of first team exposure)
So, get the cheque book out basically as "the rest" will only bring in about £50-60M tops and, by my reckoning we need to sign about 12 to 15 players over that timeframe. Let's say £300M NET SPEND is needed to get close to the top 4.