commodity research? commodities are dead. if you are a commodities researcher, he only thing you will be researching is morgues, because that is where you will be - amongst the dead.
equity research roles can be hugely dependent on the bank. i once worked in a research role in a bank but it was to do with exotic option prices and arbitrage using filters - you won't find this stuff in the modern day - some research roles require no quant
learn the major equity indices - how they behave (drift, volatility, skew, kurtosis, autocorrelation, daily/monthly trends, macro events), correlations with each other indices and with other key risk factors - 10 year UK/US yields, 2Y german yield, EURUSD rate...
funds will use some form of component analysis on their long/short equity funds - the hedging strategy on their portfolios will boil down to buying/selling maybe 4 or 5 risk factors - these risk factors will be the ones that have the largest principal components when PCA is performed on the portfolio. in mathematical speak, the eigenvalues of the risk factors will be important. so, unfortunately, some math will be required for equity research.
from a pricing/trading perspective, learn how prices are quoted - sometimes vols are quoted, other times prices are quoted. learn the Black Scholes pricing model and if you want to be rigorous learn the Dupire local volatility model. most equity research roles only cover equity stocks, forwards, futures, some other vanilla instruments and at MOST a quasi-vanilla option. so obviously you should know the details of these products. learn their greeks, their intrinsic properties, market conventions. this is not necessarily technical but books will help you here. i have never heard of an equity researcher preaching to me about variance swaps or barrier options or cliques - so dont worry about complicated equity derivatives.
i once built an implied risk neutral density function and an implied physical measure density function for some major equity indices and observed the trend - how did the extreme quantiles look? it was helpful but clients dont care for that kind of stuff. that is just one thing you could do - it is helpful to display in charts, people love looking at bell curves.
crucial to write good RESEARCH reports, advising most clients is tough at best of times. the advice here is simple: lots of charts, no or very few equations, use two columns for a page, always offer a simple conclusion. use lots of metaphors. forget the history of derivatives - this is not harry potter - not a literature book - be concise, please. look at the current 'great' researchers - here is a link to a good researcher at JPM - his style of writing is popular and is actually decent
JPMorgan Goes In On Bitcoin: Kolanovic Asks "Are Cryptocurrencies A Pyramid Scheme?" | Zero Hedge
always remember the reports you send out. you dont want to contradict yourself - actually maybe this is like a harry potter book, all your notes and reports should build into a little 'technical' manual, an evolving story of some sort, until the next financial crisis, of course, where all equity researchers will be fired anyway !